The scene is set for an almighty showdown at the EU summit starting tomorrow. The wise British decision on Monday, to limit the powers of an EU foreign minister, was promptly followed by a joint French-Spanish declaration insisting on the abolition of the veto in no less than 51 policy areas. Meanwhile, Germany and Poland are locked in a bitter battle which was not resolved by the four hours spent by the German Chancellor on the phone to the Polish President on Saturday. Warsaw is proposing a voting system based on the square root of each country’s population, backed by 28 pages of calculations, which would give it six votes to Germany’s nine. Germany is resisting any change to its preferred voting system, which, being proportional to population, would give it significantly more votes than any other state.

Is the EU falling into chaos? That is a prospect that would delight those who were naive enough to hope that an EU constitution, voted out by the Dutch and French two years ago, was dead. There will be enormous pressure on Britain to cede authority to Brussels and to resort to euphemism to disguise the extent of the concessions. There is a twist of pride and vanity in all EU summits which can generate a determination to do a deal at almost any price. Angela Merkel needs a result because she is chairing the summit. Tony Blair wants to tie up loose ends as he bows out. Nicholas Sarkozy is desperate to avoid a referendum that could distract his first term in office.

There lies the danger. Mr Blair has described four “red lines” which he says that Britain will not cross. The tactic is cute – not just lines in the sand, but red lines; the problem is that these lines seem to wobble and waver, and all will depend on whether Mr Blair sticks to the script agreed with the British public:

(1) Charter of fundamental rights Moves to make these employment law and social provisions legally binding would seriously undermine Britain’s labour market flexibility and competitiveness. The enshrinement of the right to strike, for example, raises the prospect of German secondary pickets flying in to harass British factories. The right to “information and consultation” would give workers co-decision powers in businesses. The British Government is resisting Mrs Merkel’s proposal to leave the charter out of the treaty, but to include a cross-reference that would nevertheless make it legally binding. The Prime Minister is seeking a form of words that would make clear that the charter cannot overrule or change British law in any way. But the devil will be in the detail: even if Mr Blair can get this principle agreed, he will need excellent legal drafting to ensure that the wording is watertight. The European Court of Justice (ECJ) will do its best to find a way past Britain’s concerns and the well-intentioned words.

(2) Control over the judiciary and policing The Prime Minister is rightly determined to resist the abolition of national vetos over criminal law, which would give the ECJ and the European Parliament jurisdiction in these areas for the first time. Such a move would open the way for the EU to give greater rights to those in police custody, for example, and to set criminal penalties for UK citizens. The ECJ has already ruled that some “environmental crimes” can be defined centrally. The Attorney-General has given warning that an attempt to harmonise the UK’s common-law system with the civil-law systems that are common on the Continent would require “significant changes to our primary legislation, for which we see no need”.

(3) An EU foreign ministerMr Blair is opposing anything that “displaces the role of British foreign policy and our foreign minister”. Many countries enthusiastically support the creation of an EU foreign minister, backed by an EU diplomatic service, who would chair meetings of foreign ministers and, they hope, forge a common EU foreign policy. This could, ultimately, threaten Britain’s seat at the UN Security Council. What is odd about Mr Blair’s position, however, is that Britain is not opposing the proposition that the Union should acquire a legal personality. This will enable the EU to negotiate and sign international treaties on behalf of its member states, restricting their ability to conclude independent agreements, for example, with the US. France and Spain strongly support this provision: Britain seems minded to let it pass.

(4) Diminution of the British veto on anything “that can have a big say in our own tax and benefits system” Despite the awkward wording, this red line is consistent with Gordon Brown’s fight against VAT harmonisation. But defined so narrowly, this red line ignores whole swaths of activity where the British veto will be curtailed. First, because any treaty is likely to move from unanimous agreement to qualified majority voting in 51 areas, including energy policy and the vaguely-worded power of “economic coordination”. Secondly, because the move to a new voting system for EU business will make it harder for Britain to form coalitions to block proposals that it does not like.

At the moment, the UK, France, Germany and Italy have the same weight in decision-making, through an identical number of votes. But the enlargement of the Union means that it is right to look again at how votes are apportioned. The proposed new system will dilute British power in two ways: first, by distributing votes in proportion to population (giving Germany a third more votes); and secondly, by putting the onus on countries to form larger blocking coalitions. This could make it harder for the UK to continue to block, for example, the Working Time Directive. (The so-called British opt-out from the 48-hour week is not statutory: it is guaranteed only by a blocking coalition). Mr Brown recently managed to water down the important Markets in Financial Instruments Directive, by teaming up with other member states. This will become harder to do in future. There is no indication that the British Government has thought clearly about this fundamental change in structure.

T he Government has a fair chance of achieving its “red lines”, (although serious legal scrutiny will be needed to verify its claims). But achieving the red lines will not negate the case for a referendum. In 2004, Mr Blair promised a referendum even though he maintained that the constitution would not alter “the fundamental nature of the relationship between member states and the EU”. Three years later, he is claiming that there “is not the same case for a referendum” if the treaty does not alter “the basic relationship between Europe and the member states”. That is not merely a volte-face. The treaty looks bound to dilute British sovereignty in some important areas, not least by giving the Union a legal personality and by enormously expanding the scope of qualified majority voting and therefore the remit of the European Court of Justice.

The coming negotiations are intended to agree a framework which will be turned into a treaty at an intergovernmental conference in the autumn. By that time, the question of referendum will fall to Mr Blair’s successor. Mr Brown recently promised a new “humility” in politics. To allow British voters to vote on a new treaty, if one does emerge from this process, would be a suitable way to set the tone of his premiership. For the truth is that the new treaty is likely to contain much of the ambiguous wording of the old. Only lawyers, not politicians, will be able to tell exactly how much power will be lost. The Poles seem to have a much firmer grip on their national interest. Perhaps that is because they have not been wearied by playing the game for so long.