London Mayor Sadiq Khan has been accused of breaking one of his key election pledges to freeze fares after it was revealed hundreds of thousands of commuters could miss out.

Mr Khan, who was elected to City Hall last month, admitted that the fare freeze would not cover travelcards or impact contactless caps, saying that such fares were not under his control.

The promise was a key part of the former Tooting MP’s election manifesto, having promised not to raise fares before 2020.

It is estimated almost half a million Londoners could miss out.

Wimbledon MP Stephen Hammond criticised Mr Khan on Twitter, saying that “most Wimbledon commuters will pay more” because of the broken election pledge.

The four year freeze will cover all single journeys made on London Underground, buses, London Overground, Transport for London (TfL) Rail, and London Tramlink.

The freeze, estimated to cost in the region of £640m, has been funded by numerous cutbacks within TfL, including a major revamp of the company’s IT services and cutting “expensive agency staff”.

According to the Mayor’s Office, Mr Khan and TfL have already identified savings to cover the first two years of the freeze.

Mr Khan, said: “My fares freeze on TfL services will make life easier for millions of people and will ensure that London becomes a more affordable city for all.

"To deliver this I am working on a root-and-branch savings and efficiencies review of TfL, cutting duplication and waste while continuing to improve the transport network for everyone.”

Mike Brown, London’s transport commissioner, said: “The Mayor has instructed us to ensure that TfL is the most efficient and effective organisation it can be.

“By changing the way we are organised, by driving efficiency in every part of our business and by looking for further ways in which to generate more non-fares revenue, we will deliver a transport network that continues to meet the needs of a rapidly growing London while keeping transport affordable.”