Britain's ASLEF train drivers' union said on Tuesday its members would take fresh strike action on Feb. 1 and 3 after rejecting a pay offer.
Earlier this month, rail industry body the Rail Delivery Group said it had offered ASLEF an improved pay offer in exchange for reforms to how the railways are run, in a bid to end a long-running industrial dispute.
"The proposal is not and could not ever be acceptable but we are willing to engage in further discussions," ASLEF General Secretary Mick Whelan said in a statement.
"They want to rip up our terms and conditions in return for a real-terms pay cut."
The Rail Delivery Group had said the offer included a backdated pay increase of 4% for 2022 followed by a further 4% pay rise in 2023, and a commitment to no compulsory redundancies over the next year.
However, it also included what the body described as "vital and long overdue" changes to working arrangements, including to Sunday shifts and training.
Teachers and 100,000 other public sector workers, including border force staff, are also due to walk out on Februaru 1 in disputes over pay.