Rail union, RMT will launch strike action across 14 train operators on May 13th after rejecting the latest offer from the Rail Delivery Group.
Following further discussions between the union and RDG, the employer issued a clarification on the offer RMT has been considering.
The RDG is now saying they would only implement the first-year payment of 5% if the union terminated its industrial mandate meaning no further strike action could take place.
Stage 2 discussions which are part of the offer made by the employer would then have to begin without the union having any industrial leverage at the negotiating table.
Our NEC met earlier today to formally reject the proposal and as a result have named 24 hours strike action for Saturday 13 May.
The union is currently re-balloting its members on the 14 train operating companies with a result expected May 4.
If the union beats all the legal thresholds for turnout and achieves a "yes" vote, it will have a further 6-month strike mandate.
RMT general secretary Mick Lynch said: "The RDG have reneged on their original proposals and torpedoed these negotiations.
“No doubt their decision is due to pressure exerted on them by the Tory government.
"Therefore, we have no alternative but to press ahead with more strike action and continue our campaign for a negotiated settlement on pay, conditions and job security.
"We are re-balloting our members and if we beat the draconian anti-trade union laws on turnout, we will have a renewed mandate for action.
"We will then put on a further programme of strike action to make the employers and the government who continue to hold the puppet strings, see sense in this dispute."
Train driver members alongside Aslef have also rejected the RDG's new offer in that dispute.