The RMT executive this afternoon agreed that a ballot of both groups will be concluded on June 25, and the union warned that failure to settle the dispute would result in a ballot of all Network Rail infrasructure and signalling staff.

Some 119 Network Rail staff employed in the area that includes the site of the Grayrigg crash have been denied their £400 bonus, while the more than 400 signallers and supervisors who took strike action over the company’s failure to honour an agreement have been docked £300.

“It seems that our strike threat has shamed Network Rail bosses into suspending part of their own massive bonus payments,” RMT general secretary Bob Crow said today.

“But the fact remains that 119 of our members working in the Grayrigg area have been effectively scapegoated by the corporate decision-makers of Network Rail, and that is unacceptable.

“If there is to be any disciplinary or criminal process as a result of the investigation that should be allowed to take its course, but in the meanwhile we expect to see all our members paid their bonus.

“That also applies to our signalling and supervisory members in Scotland, who were forced into taking industrial action by a management that had reneged on a deal we had signed in good faith.

“If Network Rail bosses want to avoid an escalating dispute they should do what they should have done from the start, and paid all our members the bonus that is due to them,” Bob Crow said.