Union leaders claim they have growing political support for its opposition to rail worker job cuts, as last-ditch talks get under way later to avert thousands of staff going on strike.
Officials from the Rail Maritime and Transport union are meeting executives at Network Rail, which is seeking to cut jobs and change working practices to allow more maintenance work to be carried out at weekends.
Maintenance workers belonging to the RMT have already voted to go on strike in protest at the 1,500 job losses, while the result of a ballot among signal workers will be announced tomorrow.
Members of the Transport Salaried Staffs Association have also voted in favour of industrial action, threatening the biggest outbreak of industrial unrest on the railways for over a decade.
The RMT said more than 150 MPs have now signed an Early Day Motion opposing the planned cuts and are calling on the government to intervene.
RMT general secretary Bob Crow said: "We head in to talks with Network Rail with the very clear intention of seeking an agreement which ends the threat of compulsory redundancies amongst safety-critical maintenance staff and which puts the safety and security of our railways above the drive to slash budgets to hit arbitrary savings targets.
"We have secured a huge pool of public and political support for RMT's 'rail cuts cost lives' campaign, alongside an overwhelming mandate from our members for action if that's what it takes to reverse these cuts."
NR says that 1,100 workers have already volunteered for redundancy and the "vast majority" of the 1,500 cuts will be achieved without the need for compulsory lay-offs.