The final battle of the Blair-Brown war will be fought in Brussels

Fraser Nelson says that Tony Blair's swansong summit next week is fraught with danger for Gordon Brown. The last thing the next Prime Minister wants in his in-tray is a new EU constitution that he has to sell to the British public For what must surely be the last time, war has broken out between Tony Blair and Gordon Brown. The surreal calm of the handover period has been fractured by a return to the bitterness, acrimony and threats that have been the dominant feature of government in the past decade. The Prime Minister has been told, rather than asked, to come back from next week's European Union summit having agreed a treaty which the Chancellor can plausibly sell to the British public without being forced into calling a referendum.

Almost all of the main EU players have now agreed a plan which resurrects the main points of the constitutional treaty voted down by the French and Dutch referendums two years ago. They want to settle it all in broad outline next week — at Mr Blair's last EU council of ministers in Brussels — then sign the new deal off perhaps as early as October. It is a careful stitch-up, almost two years in the making.

Would Mr Brown really pull the plug on all this as his debut on the European stage? Mr Blair thinks not. He has his own wish list ahead of the summit, concerned with wording, opt-outs and the finessing of legal language. As ever, he would be happy with half of his objectives. But Mr Brown is demanding he returns having made no concessions at all. 'It's a nightmare,' says one of the remaining No. 10 staffers. 'Ifs like the TB -GBs all over again.'

Mr Brown's anger is driven by anticipation of a potentially dire dilemma. His pitch as incoming Prime Minister is that he will be more transparent, open and honest than the shifty, grinning con-artist about to depart. There will be no more diktats cobbled together on the sofa, we are told, no more deals pieced together by backroom advisers. He promises to devolve power to the citizen and act as a tribune of the people, 'a voice for communities far beyond Westminster'. Yet it is possible, as things stand, that one of Mr Brown's first tasks as Prime Minister would be to push through Parliament a crucial EU treaty without consulting the electorate in a referendum: a spectacle that would be the very antithesis of what Mr Brown purports to believe in.

For the Conservatives, all this offers scope for the most tremendous political mischief, should David Cameron decide to make it an issue. I am told he is keen to do so, welcoming the chance to unite his party after the grammar schools fiasco. Officially, he says he will only call for a referendum if British powers are to be transferred to Brussels. But it is already fairly clear that this condition will be met.

Take, for example, the plans to end the rotating presidency of the EU and install a permanent European Commission president with 3,500 civil servants at his or her disposal. There are also proposals, advanced by France, to have the president directly elected.

The holder of the new office would turn up at the White House as the president of Europe, negotiating foreign and trade policy. The creation of such a post, first proposed in the old constitution, would in itself mark a transformative moment in the history of Europe's power grab.

Next, there would be an EU Foreign Minister whose eye would be on organisations like the United Nations. Mr Brown may argue that this would not diminish the stature of Britain's Foreign Secretary on the world stage. But the wonderfully indiscreet Denis MacShane argued differently two years ago when he was Europe Minister. 'The voice of the future EU Minister for Foreign Affairs will be louder than that of the ministers of each nation,' he told Le Figaro.

There may be a fudge of nomenclature: an EU 'International Spokesman' rather than a foreign minister. But this would matter little in practice as Romano Prodi, the Prime Minister of Italy, has conceded. 'As long as we have more or less a European Prime Minister and a European Foreign Minister, then we can give them any title,' he says. The end result is that, should this treaty be passed, the EU would finally be able to flex its muscles on the world stage as a distinct constitutional entity.

Perhaps the most controversial suggestion, however, is the new voting structure that would make it harder for individual states to block legislation. In addition, opting out has served Britain well over the years: the Department of Trade and Industry estimates our exemption from the Working Time Directive (the 48-hour working week) is worth £9 billion a year. 'This opt-out is pivotal to Blair and Brown,' says one adviser. 'If Blair can make this permanent, he will.'

But what of preserving Britain's policymaking independence in the future? The EU's voting methods are wrapped in such Byzantine complexity that it has taken a study by academics at the London School of Economics to decipher what the proposed changes would mean for Britain. Their conclusion? ,4D271/ ,4N'271 is 0.719. Or, in other words, the UK will lose just under 30 per cent of its ability to block legislation. It is the classic EU manoeuvre: disguise a straightforward power grab in the most mind-numbing formulae and protocols.

And here, should Mr Cameron miss it, is the bit where Britain hands over powers. Simply put, the streamlined Euro voting system means the British government would be forced to enact more laws sent from Brussels. It would need more allies to avoid measures like the Working Time Directive. Mr Blair sees this as a small threat: Europe, he believes, is moving in his direction. And wouldn't it be great, he reasons, to force through a single market in services? Mr Brown, however, takes a bleaker view of the negotiations ahead.

Here lies a fundamental difference between them. Mr Brown's interest so far has been in keeping Britain safe from what he sees as the EU's more dangerous ideas. He has little concern for the French and the Germans: if the rest of Europe wants to ignore his advice, well, it's their funeral. The failures of the Continental economies have been grist to the mill of his Budget speeches. Mr Blair, by contrast, is a committed European who sees a providential role for Britain in the EU — he still talks of our European 'destiny' — and genuinely believes he can steer the EU to a more pro-market path.

This is why there is such excitement in No. 10 about next week's summit. Angela Merkel, the German Chancellor, who will chair the gathering, is already implementing some economic reform in Germany, and Nicolas Sarkozy won the French election planning what he describes as a Thatcherstyle revolution. 'It is an incredible window of opportunity,' says a No. 10 official. `Sarkozy and Merkel are both pro-reform. Things are moving Blair's way. To have the three of them sitting together will form an incredible power dynamic.'

But will the same not be true for future summits, with Mr Brown in charge? The feeling in No. 10 is that he lacks the diplomatic skills — and has no interest in the European game which has fascinated the Prime Minister for so long. 'Blair would spend hours in No. 10 calling any European leader you wanted him to,' says one Foreign Office source. 'He'd really put in the effort. Brown's attitude is more, "Here is the moral high ground, and there I sit." ' They are waiting for him in Brussels. The President of the European Commission, Jose Manuel Ban-oso, told The Spectator last July that Mr Brown would have to change his tactics — or, as he put it, 'You cannot go to a beefeaters' club and say you are a vegetarian. You have no influence.' His rather touching assumption is that Mr Brown will seek as much influence in Europe as Mr Blair has done, and is driven by the same desire to save the EU from itself. Yet all the signs point in the opposite direction.

The office layout inside No. 10 may not sound like the most pressing issue facing the incoming 'administration' (as Blair's outgoing aides call the Brown regime). But to those in Whitehall, like the factions at a Tudor court, such matters have the greatest symbolic importance. The plan is that Simon McDonald and Jon Cunliffe, Mr Brown's foreign policy adviser and European adviser respectively, will not sit in No. 10 like their predecessors, but in the Cabinet Office alongside Jeremy Heywood, his new domestic affairs adviser.

Logistically, it means they will be three minutes away from the Prime Minister's office rather than 20 seconds. In the power game of Whitehall that's light years: the door which connects No. 10 to the Cabinet Office marks the crucial threshold between inner and outer circle. Mr Brown's aides argue that this shows that normal business is being resumed. No more Blair-style government within a government. Sir Humphrey is being invited back in from the cold.

That is only one way of looking at it: the Whitehall Kremlinologists conclude that Mr Brown is now happy to leave Europe to the Civil Service machine. One diplomat who has served both men says he suspects Mr Brown is entirely focused on winning the next British general election and will see every policy — domestic and foreign — through this prism.

'Faced with a choice between Sarkozy and Merkel on one hand, or Dacre and Murdoch on the other, Gordon will go with the latter,' he says. Mr Brown has so far been careful to cultivate a good relationship with Paul Dacre, who edits the Daily Mail. He will be in no hurry to start his premiership waging war against the newspapers he has spent so much time wooing, all of which are very likely to demand a referendum.

Mr Blair was saved from holding such a vote by the referendums in France and the Netherlands. But history is not set to repeat itself. President Sarkozy is an enthusiast for the new deal and is unlikely to hold a referendum in France. It is a closer call for the Dutch, but the government will do all it possibly can to avoid consulting the public. Ireland is constitutionally obliged to hold a referendum in such circumstances, but is unlikely to say 'No' on this occasion. That leaves Britain, which has not been consulted on the European Question since 1975, when it voted to stay in the EEC.

Mr Blair always believed he could win Britain round. 'It's just a case of mobilising support,' he would say to incredulous aides. His strategy would have been to misrepresent the referendum, saying that the question it really posed was whether Britain wanted to be in or out of the EU as a whole. He hoped that, by the time the issue was put to the British people, every other country would have signed up, enabling him to sell the vote as a choice between isolation or engagement. In the event, the vote was never held, and Mr Blair was denied the great reckoning on Europe that he had always craved.

Two years on, it would be a brave Prime Minister who asked the British people whether they wanted to stay in the EU or leave altogether — given that the European Commission's own research shows just 34 per cent of the British public consider EU membership 'a good thing'. This is the lowest figure in the entire 27-member union.

Mr Barroso's latest advice for Mr Blair is to ignore public opinion, or 'some of the populisms we have in our member states', as he put it on Tuesday. The Prime Minister is uniquely placed to do just that as he steps at last from the realm of day-to-day accountability into the long years of political retirement. He will appear at his final Prime Minister's Question Time a week on Wednesday, then walk into the political sunset — leaving rows about sovereignty, referendums and newspaper editorials behind him once and for all. And Mr Brown will be left with the worst welcome present of all, wrapped in the distinctive blue and gold stars of the European flag.