A project to build the UK’s largest road tunnel has been granted £590m by the government.

Constructing the Lower Thames Crossing, linking Tilbury in Essex and Gravesend in Kent, will cost an estimated £10bn.

Plans for the 14.5-mile (23km) route were approved in March after a 16-year process that has already cost £1.2bn.

Chancellor Rachel Reeves said the crossing would aid “smoother, less congested passage of vital goods from Europe to our regions”.

It came as part of a £1bn package, announced on Monday, to improve transport infrastructure across England.

The government said it was looking to source private finance to build the Lower Thames Crossing, branding it a “national priority”.

National Highways hoped the road would reduce traffic at the Dartford Crossing by 20%.

Construction was expected to begin in 2026, ahead of an expected opening by 2032.

“This is a turning point for our national infrastructure, and we’re backing it with funding to support thousands of jobs and connect communities,” Reeves said.

Transport Secretary Heidi Alexander added: “This project is essential for improving the resilience of a key freight route and is critical to our long-term trade with Europe.”

However, Treasury minister Emma Reynolds struggled to answer questions about the project on a national radio programme.

Speaking to LBC’s Nick Ferrari, she mistakenly called the existing crossing the “Dartmouth tunnel” – instead of Dartford – and could not “recall the landing zone” when asked where the new crossing would be located.

Pressed on the cost, Reynolds said “it’s going to cost quite a lot of money”, suggesting it would be “several billion pounds”.

National Highways has estimated the cost will be between £9.2 billion and £10.2 billion, depending on the funding model chosen.

The road will link the A2 and M2 in Kent with the A13 and M25 in Thurrock, and will stretch from the east of Tilbury to the east of Gravesend.

About 2.6 miles (4.2km) of the route is to be underground, with northbound and southbound tunnels running next to each other beneath the Thames.

The funding announcement was welcomed by Logistics UK, which represents the transport and logistics sector.

“Efficient logistics with minimal delays is critical to the delivery of the government’s growth agenda, and our members are delighted to hear that funding has been made available to start work on the long-planned Lower Thames Crossing, after a decade of holdups at this vital interchange,” said policy director Kevin Green.

“It is imperative that the government also sets out a plan for providing and securing the full funding required to complete the project – our members deserve to be able to deliver efficiently for the industry they support, so that the economy can benefit.”

However, campaigners have raised concerns about ancient woodland being impacted by the works.

Chris Todd, director of Transport Action Network, previously said the decision was “absolute madness”.

He added: “The only way that the government can afford this white elephant would be to take money from all the other nations and regions in the UK.”