Bringing Crossrail 2 to Tooting Broadway would cost £1bn, according to the project’s managing director.

Michele Dix, a Transport for London (TfL) director, has confirmed in a letter to Tooting MP Sadiq Khan that connecting the service through Tooting Broadway station would cost £1bn, double what it would cost to bring the route service through Balham.

In addition, the work would take eight years to complete, instead of five to six years as estimated in Balham.

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Mrs Dix said: “While we have not formally removed Tooting Broadway from the Crossrail 2 proposals, there are very significant challenges to building a station there.

“As a result, our current proposals include a station at Balham which, on balance, we believe provides a better overall solution for the area.

“We are working to develop a single preferred option for the Crossrail 2 project before the summer of next year.”

Part of the reason that costs would double in Tooting is that a large station box would need to be built from the top down before tunnel boring machines could pass through. Mrs Dix added the ground would need to be frozen to build the station tunnels.

In Balham, more of the station could be built underground, which is faster and cheaper.

The letter said building in Tooting Broadway would require worksites impacting Sainsbury’s, South Thames College, retail units in Mitcham Road, and some to the north of the station by Tooting High Street and Upper Tooting Road.

There is also a possibility that Tooting Market would be affected and that the road network in Tooting would suffer greater impact than in Balham.

Dan Watkins, Conservative spokesman for Tooting, said: “TfL’s initial ground surveys show a very large building site will be required in the heart of Tooting.

“This gives me more cause for concern than the increased cost, because that can be justified through the much greater economic benefits that Tooting would experience as compared to Balham.

“We need more information from TfL on the disruption Tooting town centre would face.

“If that requires a further study from TfL then so be it. This decision is so important that it absolutely must be got right.”