A review of outer London buses will take five years to complete, prompting outrage from politicians across the party divide.

The Mayor of London has now been accused of a "broken promise" for failing to prioritise transport in the outer boroughs.

With bus use falling across the capital, Transport for London (TfL) recently reviewed inner London routes, making reductions to underused services.

These cuts will then be redistributed to outer London, where demand for buses remains higher, according to a TfL planning document.

The transport network is now reviewing services in key pockets of outer London, varying from entire boroughs to small town centres.

But with this patchwork approach, it will take far longer to make changes across the whole of outer London than it did for inner London. TfL expects the project will take five years to complete.

Liberal Democrat assembly member Caroline Pidgeon, former chair of the London Assembly's transport committee, said more buses were needed in outer London.

She said: “The Mayor and TfL have always defended cutting bus services in central London on the grounds that buses will be redeployed to outer London.

“It now seems that only part of that deal is being honoured – that of cutting bus services in central London.

“This broken promise is another example of Sadiq Khan’s poor record in running TfL. This is not what Londoners expected when they elected a son of a bus driver.”

Navin Shah, the Labour assembly member for Brent and Harrow, said TfL’s approach to reviewing outer London services was “not good enough at all".

He said: "This approach is not going far enough and it’s very piecemeal. We need a properly planned strategic network that will not only address current problems but also how the bus network of the future will accommodate a growing population."

Mr Shah said that without better bus links, residents of outer London would remain reliant on cars, and be less able to take up new job opportunities in their area.

Geoff Hobbs, director of Public Transport Service Planning at TfL, said: “We are committed to increasing bus services in outer London and are reviewing at least seven areas in outer London each year to enable this growth.

He added: "This ongoing programme of reviews, along with our regular assessments of bus services, will result in the whole network being reviewed.”