Sadiq Khan has been urged to reveal what it would cost to cancel the controversial Silvertown Tunnel by members of the London Assembly.

The Silvertown Tunnel is a proposed river crossing that will connect Greenwich and Newham via a road under the River Thames that has been the subject of fierce criticism from locals, environmental campaigners and politicians who have said it will increase traffic and contribute to poor air quality in the area.

Despite calls from members of his own party to call off the project, Sadiq Khan has insisted it is going ahead and has said that scrapping the tunnel would “not be an option that is sensible” owing to the potential financial loss that it would incur.

In 2019, TfL awarded a contract to the Riverlinx consortium to design, build, finance and maintain the Silvertown Tunnel at an estimated cost of £2.2 billion over its lifespan.

The cost of cancelling the contract is unknown to the public or to most members of the London Assembly owing to “commercially sensitive information”.

But at a meeting of the London Assembly on Wednesday, members voted in favour of a motion that called on the Mayor of London to finally publish the details of the contract to inform further debate on the tunnel.

Green Party Assembly Member Sian Berry, who proposed the motion, said that she will “look forward to getting the openness that Londoners deserve from their mayor”.

Ms Berry said: “The Silvertown Road Tunnel is the biggest infrastructure project that the mayor has authorised. This is a huge new road project with a huge budget and huge implications for Londoners’ wellbeing.

“The ability of the London Assembly to amend the mayor’s budget is an important power. But we can only use that power, and propose and debate changes to these plans, if we are able to discuss a broad estimate of the cost of pausing or cancelling them.”

Although members of the Labour group on the Assembly did not vote in favour of the motion, they did abstain from the vote to allow it to pass.

Labour Assembly Member Len Duvall, who represents the borough of Greenwich where work has already begun on the tunnel, said that “with some creativity” the cost of cancelling the tunnel could be made public for the sake of transparency.

Mr Duvall said: “Let’s be very clear, this project is proceeding. [GLA Oversight Committee] members have been told what the costs are privately. I have a view on that… that it should be open, and we should be able to debate it. There is this issue of commercial confidentiality but, with some creativity, why shouldn’t we have that conversation of whether it can?”

Sadiq Khan has insisted that there is an “urgent need” for the Silvertown Tunnel to go ahead to ease congestion from the nearby Blackwall Tunnel, and that he does not expect traffic to increase as a result of the tunnel if a toll is imposed.