The Prime Minister told EU leaders in Dublin earlier this month that if, as expected, the European Court reaffirms the 48-hour-week Working Time Directive in an imminent judgment, he would require a treaty amendment to override the verdict of the court.
He is also demanding an end to fisheries quota hopping, the system which allows the Spanish to buy up British allocations. Again, if necessary, he is demanding a treaty change.
When Mr Major negotiated the Maastricht Social Chapter opt-out in 1991, it was agreed that health and safety provisions would not be used as a back-door method of introducing employment legislation such as the Working Time Directive.
That principle is now in jeopardy. The Government regards the directive as a direct breach of that agreement and Mr Major told a Confederation of British Industry dinner last May: "If old agreements are to be broken, I do not see how we can reach new agreements."
Ministers have been warned, however, that some EU members would veto any treaty change to satisfy the British on that question.
Cabinet sources said in Bournemouth last week that the Prime Minister had decided there could be no deal on the latest round of European inter-governmental talks, due to be settled in Amsterdam next June, unless and until that route to "backdoor socialism" had been closed.
If that was the case, Mr Major would retaliate - directly vetoing any new treaty based on the current intergovernmental negotiations. That opens the way for a conflict which would reverberate through all sessions of the inter-governmental talks in the run-up to December's Dublin summit, and beyond, in the run-up to the British election next May.
However, Malcolm Rifkind, the Foreign Secretary, went further in an unreported lecture delivered on the Bournemouth fringe of the Tory party Conference last Thursday. Twisting the British knife in a way that will incense some EU members, Mr Rifkind warned that if they wanted to pursue further political integration that was a matter for them. He then added, however, that there would be no question of partners forcing a further British opt-out from Brussels agreements. They were the ones who would have to opt out because Britain would veto any treaty change allowing them to use European institutions as a vehicle for their federal plans.
When it sinks in, that threat will incense some of the more federalist leaders.
Nevertheless, Mr Rifkind said: "Flexibility must not lead to a two-tier Europe; of first- and second-class nations. That would be a betrayal of the wider European ideal and a sure recipe for tension."
"It may be that some states will wish, in their own national interests, to proceed with closer integration. So be it. But because that would have implications for all of us, it could only proceed using European institutions if all agreed," Mr Rifkind said. The British Government would not agree; it would veto any such change.
Mr Major also warned EU colleagues in Dublin this month that he will not tolerate the continuation of fisheries quota hopping. "If the present treaties don't allow us to correct the abuses that presently exist under the Common Fisheries Policy, then the treaties must be changed". As with the Working Time Directive, it is most improbable that Mr Major will win unanimous endorsement for his demands on fisheries policy. Without unanimity, there can be no treaty change.
But, given the Tories' tough stance against EU development while portraying Labour as a Brussels pushover, any confrontation will play straight into Mr Major's hands in the lead up to the next election.
Given Tory divisions, the impending battle with the EU could be fraught with risk for the party high command. But a calculation has been made that the strategy is much more likely to please the Euro-sceptics than to provoke the Heathite "grandees" into fresh open protest. It is believed that as the pro-Europeans are more loyal to the leadership, they are more likely to keep quiet about Mr Major's new anti-EU confrontation, for fear of being blamed for opening up new splits and criticising the Prime Minister on the eve of a critical election.