Fresh Tube strikes could take place next month as staff are 'split' over whether to accept a five per cent pay rise.
Tube drivers could stage another round of walkouts in the new year, after members of the Rail, Maritime and Transport (RMT) Union could vote to reject the pay deal.
It comes despite 88% of drivers belonging to the Aslef union voting to back the TfL deal.
But the offered pay increase will only go ahead if backed by all unions, with fresh stoppages likely in January if RMT members elect to reject the deal, with the results of its ballot due next Tuesday, the Evening Standard reported.
RMT's leadership described the latest offer, the result of months of negotiations between unions and TfL since May, as a 'pay-cut'.
More tube strikes could go ahead next year as unions are split over whether to accept TfL's offer of a five per cent pay rise
RMT union, which represents 10,000 workers, is pushing for a pay increase of 11 per cent in line with inflation in April
Its main account on X reposted a message from its Bakerloo line leaders saying: 'Five per cent is a pay cut, strike to win a better deal!'
The union, which represents 10,000 workers, is pushing for a pay rise of 11 per cent in line with April's inflation figures, with a minimum increase for the lowest-paid of £5,000.
The TfL situation is in contrast to the ongoing National Rail dispute, in which Aslef members have voted to continue with industrial action, while RMT have accepted an offer.
London Underground drivers are on a fixed £63,901 per year, around double the salary of some station staff.
TfL's commissioner Andy Lord said the current deal was the 'highest that can be offered'.
Aslef's London Underground organiser Finn Brennan said that any further delay could create tax burdens for workers and potentially cause problems for drivers planning to retire.