Rail union RMT say there could be "another Hatfield" after releasing a picture of a six inch gap in the East Coast Mainline track near Selby.
An investigation's been launched by the Rail Accident Investigation Branch after the picture was taken last Friday at Hambleton South junction, and the union says it is due to staffing cuts.
An investigation found the Hatfield crash - which killed four people when a train travelling from London to Leeds derailed in 2000- was caused by "critical cracks" on the track.
RMT say a crack near Selby, due to staffing cuts, has crumbled to a much bigger gap.
RMT claim there is massive pressure from the Government to keep the East Coast Mainline running, as they look to re-privatise the service. They say there are also demands on Network Rail from the budget-holder, the Office of Rail Regulation, to cut back on rail renewals work.
Network Rail strongly deny the claims and a dip was identified - but it turned into a crack the day before they were due to repair it.