A contractor has been picked to help build the UK’s longest road tunnel.

The Lower Thames Crossing aims to tackle congestion problems at the Dartford Crossing by constructing 14.3 miles of new road and a 2.6 mile tunnel linking Kent with Essex.

If approved, the £9bn road and tunnel link, which will run beneath the River Thames, near Gravesend, will connect the M2/A2, A13 and M25.

National Highways has today announced French engineering firm Bouygues Travaux Publics has bagged the contract to bore the tunnels.

They join a team that already includes Balfour Beatty, who will build the roads north of the Thames under a £1.2bn contract, and Skanska who will be responsible for roads in Kent for £450m.

To date, around £800 million has been spent on the major infrastructure project – with costs for the total project confirmed to be rising to £9 billion.

Lower Thames Crossing Executive Director, Matt Palmer, says the “world-class team” has “carbon reduction, community and value at its heart”.

He said: “By bringing the team together at an early stage we can focus on driving out carbon, delivering the best possible value for money and maximising the huge benefits the project will deliver nationally, regionally and locally.

“Bouygues Travaux Publics – Murphy JV and all of our delivery partners are fully bought into our passion for delivering a green-skills legacy and share our ambition to use the Lower Thames Crossing as a catalyst to change the whole construction industry’s attitude and approach to carbon reduction.”

However, an estimated start date for the construction of the Lower Thames Crossing has been pushed back by two years by the government

It comes amid concerns over the escalating cost of the project and its environmental impact with a small area along the proposed route redesignated as ancient woodland.

The Prime Minister’s decision to scrap part of the HS2 project in October also cast further doubt over the project.

Its choice of location has also come under fire from Gravesham council who oppose the siting of the crossing.

The leader of the council, Cllr John Burden, said at a council meeting in June that the authority continually opposed the move due to “the impact it will have on our local residents, businesses and the environment”.

But National Highways, who are developing the new route, say it will help grow the economy across the UK by almost doubling road capacity across the Thames east of London and make journeys across the region quicker, safer and more reliable.

Dartford council’s leader Jeremy Kite (Con), who is in favour of the scheme, has slated recent delays as “dreadful for local people”.

Speaking previously he said: “We’ve just got to get on with this and I hope the government will see through these objections.”

The plans are being assessed by the Planning Inspectorate, and if approved, work could start in 2026.

National Highways hopes it will open to traffic by 2030.