Chris Grayling, the Transport Secretary, accused the unions of "trying to turn back the clock" and making "excuses to be militant" by holding strikes over "pretty minor matters".

He said: "I'm very disappointed that unions keep on calling strike action over what always appear to be pretty minor matters, not to do with passengers, not to do with jobs.

"This feels like an excuse to be militant. The unions are trying to turn the clock back and hang on to working practices that are decades out of date. This simply won't do."

Manuel Cortes, general secretary of the TSSA, confirmed earlier this month that action was being co-ordinated with "our sister rail unions to maximise the impact".

He told The Telegraph: "We talk to all the trade unions on the railways.

"Our view is that the Department for Transport is telling companies who are taking over new franchises to introduce measures which will cut safety.

"Chris Grayling is just trying to pour petrol onto the fire. If those are the kind of comments he is going to make then, he should just keep his trap shut."