Douglas Hurd, the Foreign Secretary, has already made clear that passing the amendment will have no legal bearing on the Government's ability to ratify the treaty.
But losing the vote will have damaging repercussions for the Prime Minister and the Government.
Labour views the amendment as a significant opportunity to embarrass the Government, but needs the support of Tory rebels to get it passed. That it is likely to get after the dissidents vowed to turn a deaf ear to pleas for party unity delivered by John Major and senior ministers at last weekend's Conservative Central Council meeting in Harrogate.
If the amendment is carried, MPs may have to sit through a report stage of the Bill, prolonging it for several weeks, to the inevitable dismay of Britain's European Community partners and further damaging the Prime Minister's credibility in Europe.
James Cran, Tory MP for Beverley and an unofficial rebel whip, said it was highly likely that the amendment would be carried. Rebel MPs would vote for it because it offered the prospect of a report stage. 'That will be an opportunity for a debate on a highly important constitutional issue,' he said.
As for the ministerial offensive at the weekend, he said: 'As far as we're concerned it's no surrender. When I woke up this morning we were still in a democracy. No amount of lecturing from ministers will change things.'
The rebels' hopes of a report stage for the Bill may be frustrated, however, if ministers seek to give assurances to the Opposition in an effort to avoid pressing the amendment to a vote.Reuse content