RMT members at Unipart Rail in Crewe defied management to push ahead with strikes today.
The workers walked out after Unipart decided to derecognise their union.
Despite the lawful vote for industrial action, RMT says managers reportedly forced the workforce into meetings earlier in the week, warning that anyone joining the picket line would face disciplinary action.
Staff were also reportedly required to sign an attendance sheet to confirm they understood these threats.
RMT general secretary Mick Lynch said: “Unipart Rail’s threats to dismiss our members for exercising their democratic right to strike are an outrage and a clear attack on all workers.
“We will not sit back while our members are threatened and bullied in this disgraceful manner.
“Unipart Rail should get round the table and discuss our members’ right to collective bargaining rather than resorting to intimidation and unlawful scare tactics.”
A Unipart spokesperson said: “The issue as to whether the proposed action is lawful is being addressed in correspondence between Unipart and officials of the RMT.”