Silvertown Tunnel view
Tunnelling work is expected to begin from the Silvertown side this summer

The London Assembly has called on Sadiq Khan and Transport for London to provide data on what would happen if a future mayor dropped tolls on the Silvertown Tunnel.

Drivers will be charged to use the new tunnel when it opens in 2025, along with the Blackwall Tunnel, with the money paying back the £2 billlion cost of the project. The London mayor and TfL, which he chairs, insist that the tolls are needed to stop roads around the tunnels being overwhelmed with drivers eager to make use of the crossing between the Royal Docks and Greenwich Peninsula.

However, a loophole in the legislation allowing the Silvertown Tunnel, which was approved in 2018, means that a future mayor could scrap the charges. Opponents of the tunnel fear that a populist politician could win power at City Hall on a platform of scrapping tolls.

When the scheme went through the planning process six years ago, no modelling was produced on the effects of the tunnel without the tolls. Today the assembly, which scrutinises the mayor’s powers, voted 12-10 in favour of asking TfL to produce this data – with Labour assembly members voting against.

Green assembly member Sian Berry, who proposed the motion, said: “This motion is not about whether Silvertown Tunnel should go ahead, this is about the assembly ensuring all projects that affect Londoners have proper assessment and transparency.

“For years, campaigners and local councillors at both ends of the potential tunnel have repeatedly called for information about what would happen if in the future a London mayor chooses to remove or reduce the tolls that are intended to keep traffic induced by the plans down.

“I look forward to seeing the Mayor respond positively to the assembly’s request for this vital information.”

Caroline Pidgeon, for the Liberal Democrats, seconded the motion. She said: “The public has a right to know how Silvertown Tunnel could operate in the decades ahead and that must mean that modelling information is provided on the health, congestion and climate consequences of there being no charges to use the tunnel.

“There is no absolute certainty that charging at the two tunnels will exist on a permanent basis so a full examination of the impact from no charges must be undertaken and published.”

Labour assembly member Elly Baker mocked the notion that a future mayor would remove the tolls. “This is a situation that doesn’t exist,” she said. TfL would have to pay back the money from stretched budgets. I’m not expecting transport to be awash with money and there’s a political context where we’re moving towards more road charging and not less.”

Asking TfL to model the effects of the scheme without tolls would “only enable further dramatic, but false, claims to be made about the tunnel,” Baker said. “There will be a toll. There is no point modelling no toll.”

But Berry said that the modelling would have be done again to enable a final decision on a toll. “We’re asking him to give us the zero number on the toll,” she said. “It’s not a lot of work – it’s something we want to know now for our job as scrutineers.”

The Tories backed the motion. Conservative assembly member Andrew Boff – who, unusually for his party, opposes the tunnel – said of Labour’s position: “It’s one of those moments where a political group decides they want to make decisions in ignorance.”

Tunnelling work is set to begin this summer, with equipment being put in place on the north bank of the Thames. Opponents of the tunnel will be holding a conference tomorrow about the scheme’s health implications.