Threats to impede progress in the Inter-Governmental Conference (IGC) negotiations are less serious, as no formal negotiations have yet begun.
However, in the next days and weeks Britain can block agreement in several key areas of European business where unanimity is required. The Europol convention now looks certain to be shelved, along with a deal on new measures to combat racism and xenophobia.
The first measure likely to be blocked is a new insolvency convention, ensuring mutual recognition by state's insolvency laws, which is due to be signed tomorrow. British officials in Brussels said yesterday they had received no instructions on how to proceed, but appeared confident that there would be no "empty chair" policy, and they would, at least, attend meetings.
The decision to go to the European Court of Justice in Luxembourg to challenge the beef ban will also cause alarm. The Commission has conceded that elements of the ban may not have been formulated on strong legal grounds. Given Britain's constant criticism of the European Court, a victory in Luxembourg would present something of political paradox.
A series of decisions on monetary union, employment and foreign policy are due to be tabled in Florence on 21 June. If Britain refuses to agree, they will not go through.
Among the issues coming up for discussion at Florence, Britain's partners have been hoping for outline agreement on how countries inside EMU will relate to those outside, Germany will want to push through proposals for a single currency "stability pact", and the Italian presidency had hoped to produce guidelines on tackling unemployment and social policy.
In the run-up to the summit the potential for disruption of everyday EU business is enormous. In areas of justice, home affairs and foreign policy, decisions are still largely taken by unanimity. Britain had been prepared to take an "opt out" on one section of the Europol convention, giving jurisdiction to the European Court. The "opt out" will now be refused and the convention shelved.
Several EU diplomats described Mr Major's statement as a product of "domestic politics", which had little to do with Europe. However, no one in Brussels was in any doubt that the threats could cause serious disruption. "This will simply lead to Britain's further alienation in Europe," said a Spanish official.
The European Commission refused to be drawn into the political maelstrom, putting out a bland statement saying it would continue to work for a progressive lifting of the beef ban.
The Commission has been an unlikely ally for Britain in recent days, as it was the Commission which proposed the lifting of the ban for gelatine, tallow and semen, only to be over-ruled by member states on Monday night. The Commission's new conciliatory approach may reflect uncertainty within the institution about whether the ban is based on firm legal grounds.
In its statement, the Commission reaffirmed that the ban should not be seen as an anti-UK measure. "The BSE problem affects not only the UK but all member states as is evidenced by the serious decline of beef market prices throughout the [European] Union. It is therefore a problem for the whole of the European Union and a solution can only be achieved through the proper functioning of the Union's institutions and procedures . . ."
French officials stressed that any "violent political reaction" from Britain would not be helpful. France supported the proposal to ease the ban, and French officials pointed out yesterday that at one point the vote was very close to being passed. When the proposal goes next before a meeting of agriculture ministers on 3-4 June, only a simple majority of eight countries is necessary.
Britain could have hoped for such a simple majority, but in view of the new threats from London many member states may now harden their position, officials in Brussels predicted. "It is a great pity that Britain has reacted like this. We were close to getting this through," said one French diplomat.
France's role in the Monday meeting, however, is viewed with some suspicion in London. The Government clearly believes that France could have done more to produce a majority, but was unwilling to alienate Germany, which was leading the "no" voters.
Germany looks certain to be unmoved by the British threats. Helmut Kohl, the German Chancellor, has refused to make any concessions on easing the ban so far. Austria has followed the German lead, as did Belgium and Luxembourg on Monday. Spain, which also opposed the easing, along with the Netherlands, looks unlikely to change its mind.
Inside Parliament, page 7
Leading article, page 15