David Cameron today faces the biggest Commons revolt of his premiership -- and potentially the biggest ever Conservative rebellion on the issue of Europe.

On 20th May 1993, 41 Conservative MPs voted against John Major on the third reading of the Maastricht Treaty. To date, this was the biggest ever Tory rebellion on whipped business on Europe.

Coincidentally, it is also the figure for the largest Conservative rebellion so far in this Parliament. Earlier this month, on 10 October, 41 Tory MPs voted against attempts to criminalise "insulting" words or behaviour. This did not make much of a splash in the news -- unlike the current vote, which has gathered attention both for the spectacle of the Tories fighting over Europe (again), and because of Cameron's belated decision to impose a three-line whip.

It is still unclear how many MPs will defy the whips to vote in favour of a UK referendum on Europe, but according to the highest estimates, it could be nearly double that 41 figure. If the list of Conservative MPs who openly pledged to support the referendum is combined with those who have already defied whips over Europe since the beginning of this government, the number is closer to 78. Separately, Sunny Hundal suggests that up to 10 Labour MPs could defy their whips to vote in favour of a referendum.

Cameron is attempting to reassure the doubters that in the event of treaty change, he will renegotiate Britain's position. The story dominating the papers this morning -- that Cameron and Nicolas Sarkozy had a heated exchange on Europe -- fits the narrative that the Prime Minister wishes to further: that he is not afraid to anger European leaders in his defence Britain's interests. However, this does not appear to be getting through to his party.

In a survey for Conservative Home, 64 per cent of respondents said that they did not believe that Cameron was "very committed to repatriating any powers from the European Union", despite his promises, compared with just 18 per cent who did believe he wanted to repatriate "significant" powers.

It is impossible to say exactly how large today's Commons rebellion will be, and, as the Ballots and Bullets blog points out, the number that actually votes against the whip is almost always invariably less than that predicted. Even if the revolt is not as large as expected, however, it is difficult to see how Cameron can emerge well from this, and one must question his logic in applying the whip in the first place. Mary Anne Sieghart argues today:

If there had been a free vote, the motion might not even have been carried. But if it had, Cameron could easily have said, "I hear what you say. I agree that any renegotiated relationship with the EU will have to be endorsed by a referendum. But it's too early to call one now, when we don't yet know what shape the eurozone will take or what any new relationship will look like." He would have sounded both responsive and responsible. Instead he has absolutely infuriated his party.

Emotions in the Tory party are certainly running high, with at least one ministerial aide -- Stewart Jackson (£), aide to Owen Paterson, the Northern Ireland Secretary -- willing to vote against the whips even if it costs him his job. Graham Brady, the head of the powerful 1922 committee which represents backbenchers, is also set to defy the government (Lord Tebbit said yesterday that "not even Ted Heath faced the chairman of the 1922 Committee voting against a three-line whip"). While the vote is likely to go Cameron's way, the damage within his party will take longer to heal.