It looks like it is game over for the PLP's serial rebels as Chief Whip Jacqui Smith brings in new disciplinary rules: http://www.timesonline.co.uk/article/0,,17129-2263140,00.html
This should have been done in 1997 not left until now.
My own MP Diane Abbott is having a good whinge about it: http://www.timesonline.co.uk/article/0,,6-2262980,00.html
I don't have much sympathy for her position. Why should there be one law for local councillors and another for MPs? On any local council you confine your policy arguments to private Group meetings, if you lose a vote in the Labour Group you support the majority position of the Group once it gets to full council, and you can have the whip suspended for behaviour that brings the party into disrepute or for voting against the Group. I've had to vote for things I disagree with because I've been in the minority - that's the nature of being in a political group rather than an independent.
There is very little point having a Parliamentary Labour Party - as opposed to a bunch of individual MPs - if it doesn't take decisions collectively, stick to them, and have effective sanctions to apply to people who won't accept collective responsibility.
The wider electorate only get one Labour candidate to put a cross next to in a parliamentary election. They don't get to express a preference for a leftwing or a Blairite MP - most voters are judging the parties on which one they want to form a government. The least they should expect is that if it says Labour on them tin it will be Labour in the tin - i.e. every Labour MP will vote for the policies that were in the Labour manifesto.
No one is trying to silence you Diane - just to get you to accept basic standards of collective responsibility that even the most junior backbench councillor signs up to.