Update: It now appears that Mike Crockart is not resigning after all. The word from the Lib Dems is that the mistake occurred because the wrong phone number is beside his name in a media directory. A spokesman for Crockart said: "The quotes were from a random man, not Mike. They had somebody else's number against his name. Mike is still waiting to see what the final offer will be before he votes and that has always been our line."

The fake Mike Crockart also appeared on the World At One and was quickly cut off after the show realised their mistake. All of which begs the question: is he the only Lib Dem imposter? It would explain an awful lot ...

Update: Lib Dem MP Mike Crockart has said that he will resign from his post (PPS to Michael Moore) in order to vote against tuition fees. He told the Evening Standard: "I will be voting against 100 per cent. I'm not going to be pushed out. Resigning probably will be the only option." Norman Baker and at least one other Lib Dem MP are also thought to be on the verge of resigning.

The dizzying attempt to chart the Lib Dem split on tuition fees continues. It's some measure of Nick Clegg's lack of authority that party unity has decreased, not increased, in the past 24 hours.

What looked like a three-way split has become a four-way split. After failing to reach agreement on a mass abstention, senior Lib Dem ministers including Clegg and Vince Cable will vote in favour of their own policy. They will be joined by pro-fees MPs such as David Laws and John Hemming.

A second group of ministers and backbenchers will abstain from the vote (as is their right under the coalition agreement). A third group of left-leaning MPs including the party president, Tim Farron, and the former leaders Charles Kennedy and Ming Campbell ("my credibility would be shot") will stick to their election pledge to vote against any increase in fees. A final group of backbenchers is pushing a fourth option of calling off the vote in order to allow a full public consultation to take place.

One of them, Greg Mullholland, told the Guardian: "Sometimes the most courageous thing to do is to admit you need a rethink. The best thing for higher education is not to force this vote through on Thursday." All of which looks like a feeble attempt to postpone the inevitable. There is no prospect of a substantially different package being put forward by the coalition.

Meanwhile, it's worth keeping an eye on the three Tory MPs who also signed the NUS pledge to vote against any increase in fees. After all, as recently as Michael Howard's leadership, the Conservative Party itself was opposed to the principle of tuition fees.

The Fees Three are: Ben Wallace (Wyre and Preston North), Lee Scott (Ilford North), Bob Blackman (Harrow East). Wallace has since claimed that the NUS "misinformed" people of his intentions but Scott (who is Philip Hammond's PPS) is still on record as opposing any rise in fees.

Here's a list of those Lib Dem MPs likely or certain to vote against the bill on Thursday:

1. Charles Kennedy ("I shall be voting against the coalition's proposals on university tuition fees.")

2. Ming Campbell ("My credibility would be shot to pieces if I did anything other than to stick to the promise I made.")

3. Mike Hancock ('It's a big step in the right direction but the government hasn't done enough to make me vote for it and I won't.")

4. Julian Huppert ("I made a promise to the students that I would never support a rise in tuition fees and I have reaffirmed that promise today.")

5. John Leech ("I again publicly state that I will vote against an increase in tuition fees.")

6. Ian Swales ("I can't support raising the fee cap up to £9,000 per year.")

7. John Pugh ("I will vote against any rise in tuition fees, unless a rabbit is pulled out of the hat – and there is no sign of that.")

8. Tim Farron

9. Bob Russell

10. Mark Williams

11. Simon Wright

12. Roger Williams

13. Martin Horwood

14. Greg Mullholland