Rail union RMT has described proposed job cuts by Carillion as a "direct threat to both jobs and safety".
The organisation has been presented with a consultation document from the Network Rail contractor this week, which indicates the company is considering job cuts and redundancies.
RMT said the "alarming and deplorable proposal" is down to Network Rail' cuts in its planned renewals programme.
"These cuts to renewals will mean the loss of skilled railway engineers' jobs and trains running on older, less safe, track," the union said.
"They expose the nonsense of the government's approach to railway funding and they show that the government's claim to be investing in rail improvement and delivery is wholly bogus."
A formal consultation on the cuts plans will begin on Friday, 26 May.
Mick Cash RMT General Secretary said: "The Government and Network Rail have a duty to ensure that our railway is maintained and renewed to the modern and safe standard that the public and our economy needs and deserve.
"The announcement of cutbacks affecting Carillion and other infrastructure companies are a sure sign of cash and job cuts that will put at risk skilled jobs and also the modern, safe rail infrastructure we desperately need.
"RMT will not stand by and watch these jobs vanish and will campaign all the way politically and industrially to protect them."
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