The policy is to be debated in the Commons today. With the Conservative majority reduced to one Opposition MPs are not ruling out a defeat for the government.
Pat Walker, of Save Our Railways, says its surveys showed many Conservative MPs were opposed to privatisation and he denied they would back down rather than sink the government.
He commented: 'This really is not a matter of confidence in the government overall. This is a matter of the national interest and the future of our national rail network.