The largest road tunnel in the UK will be built after a £9bn plan was approved by the government.

The Lower Thames Crossing would link Tilbury, Essex, and Gravesend in Kent by two tunnels running underneath the River Thames.

National Highways hoped the road would reduce traffic at the Dartford Crossing by 20% and open by 2032.

Jim Dickson, the Labour MP for Dartford, said the decision would “finally deliver a solution to the traffic chaos” faced by motorists.

The 14.5-mile (23km) road would link the A2 and M2 in Kent with the A13 and M25 in Thurrock.

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

Tuesday’s announcement was 16 years in the making, with the project first mooted in 2009 and more than £1.2bn in taxpayers’ money spent on planning since.

The application was submitted to the Planning Inspectorate for consideration by National Highways on 31 October 2022.

It was approved by Secretary of State for Transport Heidi Alexander on 20 March.

National Highways has planned to begin construction in 2026.

Dickson said: “For far too long governments have dodged making a decision on the Lower Thames Crossing, leaving Dartford residents to endure endless gridlock.

“Now under this Labour government, the new crossing has finally received the green light and will be built.

“This decision will unlock economic growth across the country and finally deliver a solution to the traffic chaos faced by my constituents on a daily basis.”

The BBC understands the decision on the funding model has not been made yet, but the tunnel itself and the utility works would be publicly funded, alongside significant private sector finance.

Chancellor Rachel Reeves said in January that the private sector could help “to deliver the infrastructure that our country desperately needs”.

Reacting to the announcement on X, James McMurdock, the South Basildon and East Thurrock MP, said congestion in Kent would remain “unresolved” despite the project.

The Reform UK MP feared miles of countryside would be “covered with tarmac” adding: “Where has our pride and ambition gone?”

Campaigners have also raised concerns about ancient woodland being impacted by the works.

However, National Highways described it as “the most significant road project in a generation”.

Executive director Matt Palmer added: “It will unlock growth with quicker, safer, and more reliable journeys.

“Our plans have been shaped by the local community and refined by robust and rigorous examination from independent experts.”