The result could be a catastrophe for Maastricht, with Denmark, Ireland and France possibly being forced into high-risk strategies of putting the treaty - modified to include Britain in the Social Chapter - to their electorates yet again. If successful, the Labour amendment would become a time-bomb ticking away at the heart of the integration process, some legal experts fear.
The Foreign Office has joined the war of words over Labour's amendment, which has presented John Major with a crisis. The battle centres on whether the amendment will wreck the treaty. Labour insists it will not; the Government and the anti-Maastricht Tories say it will.
Tristan Garel-Jones, the minister of state, told the Commons it would mean the treaty would have to be renegotiated, though he conceded it might be possible to do it at an intergovernmental conference in 30 seconds. But he warned that attempting to renegotiate the treaty, even for something which the other 11 member states favoured, would put it in peril.
'If the amendment is successful, the UK will have failed to ratify the treaty' - opting in to the Social Chapter Protocol would amount to a modification of the treaty and would require further ratification, said Colm Mac Eochaidh, who directs the Brussels office of The Law Society of Scotland, England and Wales.
When Mr Major returned from the Maastricht summit proclaiming 'game set and match for Britain' because he had blocked the Community from including the Social Chapter in the treaty, it was little noticed that he also ensured there was no 're-entry clause' for Britain. This contrasts with the Danish opt-out from monetary union.
The Social Charter was conceived by Jacques Delors as a way of improving working conditions as companies profited from operating Europe-wide. The Social Charter - which Britain was not party to - was only declaratory in effect, and moves to insert a Social Chapter in the Maastricht treaty were blocked by Mr Major. The compromise negotiated by Mr Major was the Protocol on Social Policy, which provided that the other 11 EC states could decide social matters without Britain taking part or being bound by any decisions.
Foreign Office advice that the amendment will wreck the treaty is being reinforced by a briefing note to Tory MPs warning of the dangers of supporting the amendment. But George Robertson, Mr Garel-Jones' Labour shadow, has received advice from member states that the amendment would only require a brief renegotiation.
The anti-Maastricht Tory MPs have taken their lead from Martin Howe, a Conservative lawyer and Euro-sceptic. In a letter to the Sunday Telegraph, he says: 'Mr Smith's amendment seeks to delete the Protocol on Social Policy from the Maastricht treaty. The protocol simply gives the UK's permission to the other 11 states to use the common Community institutions for administering their separate social agreement.
'Deleting the protocol would mean that the other 11 would have to administer their social agreement through their own separate institutions . . . (the) amendment would further distance the UK from the Social Charter . . .'Reuse content