Expanding London Mayor Sadiq Khan's controversial fares freeze to include Londoners' travelcards would cost City Hall a total of £132m a year.
Khan campaigned on the basis of freezing the capital's travel costs for four years, but it later emerged that this would affect only a limited selection of travel costs.
Only single and pay-as-you-go fares are including in the programme, with the mayor attributing the exclusion of travelcards, in part, to the use of services outside of Transport for London’s scope.
However, a Freedom of Information request filed by City A.M. shows that City Hall could expand the pledge, at a cost.
In a briefing put together by TfL, it is revealed that the cost of including travelcards in the fare freeze "would be an additional £660m over five years", or equivalent to £132m per year.
By comparison, TfL stated in March last year that it expected annual income of £10.4bn for the year 2016/17.
Conservative London Assembly member Keith Prince said: “From the minute it emerged the Mayor’s fares freeze would fall well short of what he’d promised, he has consistently claimed he could do no more.
“He has repeatedly insisted he cannot freeze all fares and was adamant that he received no fares advice from Transport for London.
“The uncovering of this document proves what many of us have suspected for a long time – that he was simply not telling the truth.
“Londoners who elected Sadiq Khan on the back of his keystone fares freeze pledge deserve an apology for this shameless approach, as well as answers to the worrying questions the emergence of this document raises.”
A spokeswoman responded for the mayor responded that travelcards, and associated daily and weekly caps, are set by the government in agreement with the private train operating companies.
"The mayor has fully delivered on his pledge to freeze all TfL fares and continues to urge government to do the same for rail fares they are responsible for in London. Both the mayor and TfL are also making the case for more suburban rail services to be transferred to TfL as quickly as possible.
"This would mean that more Londoners would benefit, and help ensure that London gets a world-class rail service."
They added: "The mayor made it clear in his manifesto that he would freeze all TfL fares and charges for the cycle hire scheme for four years."