Members of the biggest rail workers union have voted to renew their mandate to strike during the next six months in the long-running dispute over pay and conditions.

The Rail, Maritime and Transport union (RMT) said staff across 14 train companies overwhelming backed taking more industrial action.

RMT general secretary Mick Lynch said the result was a de-facto referendum on the pay offer that has been put to them.

“It is clear from these results that members are not prepared to accept a pay offer based on mass job cuts and major attacks on their terms and conditions,” he said.

“This sends a clear message to the employers that the huge anger amongst rail workers is very real and they need to recognise that fact, face reality and make improved proposals.

“They need to get around the table with RMT and negotiate in good faith for a better deal for rail workers.”

Unions involved in disputes have to re-ballot their members every six months to legally continue with strikes and other forms of action.

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The RMT has already announced a strike against train companies on 13 May, the day of the Eurovision Song Contest final in Liverpool.

The decision came after the union rejected a pay offer from the Rail Delivery Group (RDG), which represents train operators, including a 5% pay rise backdated to January last year and a 4% hike for 2023.

The RMT called it “dreadful” and said changes to working practices would make railways less safe and result in thousands of job losses.

While negotiations to reach a new deal were underway, last week the RMT claimed train operators “torpedoed” talks by saying they would only implement the first-year payment of 5% if the union terminated its industrial mandate.

The RMT said that would remove its “industrial leverage at the negotiating table” and it had no choice but to strike.

Train drivers from the Aslef union, who are involved in a separate dispute with the RDG, have also announced strikes on Friday 12 May, Wednesday 31 May, and Saturday 3 June – the latter on the day of the football cup final and the Epsom Derby.

But the RDG have called the action “unnecessary” and accused the unions of “senselessly targeting both the final of Eurovision and the FA cup final”.