A decision on the £9 billion Lower Thames Crossing will not be made until May.

Transport Secretary Louise Haigh said in a written statement to Parliament it was “necessary” to extend the deadline for a decision on the controversial route - which would have provided a link, under the Thames, from east of Gravesend to the M25 in Essex.

Ms Haigh said the decision would give more time for the application to be considered, including “any decisions made as part of the spending review”.

The initial deadline for a decision on whether to grant a development consent order enabling National Highways to build the 14.3-mile road was scheduled for June 20 but was put back until October 4 because of the general election.

It was again expected on Friday, but was delayed as Parliament was on recess due to party conferences.

Ms Haigh said: “This statement confirms that it is necessary to extend the deadline for a decision on the application by National Highways under the Planning Act 2008, for the A122 (Lower Thames Crossing) development consent order.”

The minister added: “The deadline for the decision is to be further extended to May 23, 2025 in order to allow more time for the application to be considered further, including any decisions made as part of the spending review.

“The decision to set a new deadline is without prejudice to the decision on whether to grant the application development consent.”

Spearheaded by National Highways, the government agency tasked with our major roads, it was revealed earlier this year that planning costs for the project - first touted over a decade ago - have already topped £300 million.

The Lower Thames Crossing proposal is aimed at reducing congestion on the Dartford Crossing with a new motorway-style road.

It would connect the A2 and M2 in Kent to the A13 and M25 in Essex via a 2.6-mile long tunnel under the Thames, which would be the UK’s longest road tunnel.

National Highways wants to start construction in 2026, with the road opening in 2032.

But a key challenge has been the enormous cost of the scheme which has spiralled since it was first proposed.

Chancellor Rachel Reeves has long repeated the mantra that the government is facing a “£22bn black hole” in the public purse as a hangover from the last Conservative administration.

However, it was thought one option which could see the project delivered, while easing the strain on Whitehall coffers, would have been through what is known as a Private Finance Initiative (PFI).

It could see a long-term contract between a private party and the government where the private sector designs, builds, finances and operates the public asset.

Investors would receive returns from the road through toll fees - likely to have be ‘free-flowing’ as is currently the case at the Dartford Crossing with its Dart Charge - in exchange for coming up with the initial capital.

Explained National Highways in its promotion for the route: “Designed to handle 135,000 vehicles a day, the Dartford Crossing now averages 150,000 a day and requires a dedicated team to manage it around the clock. The huge numbers of vehicles that use it each day make it one of the country’s most unreliable roads, causing misery for millions of motorists and acting as a handbrake on the economy.

“Congestion on the Dartford Crossing costs the UK more than £200 million every year in time lost sitting in traffic.

The route would include 2.6 miles of tunnels - two in total, one south, one northbound - under the Thames. At 16 metres wide, they would have been some of the largest bored tunnels in the world.

They would be located to the east of the village of Chalk on the south side of the Thames, and to the west of East Tilbury on the north side.

However, the scheme has been met with fierce criticism.

The Kent Wildlife Trust is one of a number of conservation organisations in raising concerns about the environmental impacts.

It said: “The project will result in the loss of ancient woodland and veteran trees. In total, nine areas of ancient woodland are threatened with direct damage and loss, including three Sites of Special Scientific Interest (SSSI), such as Shorne and Ashenbank Woods SSSI.

“The country is facing an ecological meltdown with only around 2.5% of ancient woodland remaining. These are unique and precious habitats that support an array of rare wildlife. You’re not just removing trees when you lose ancient woodland, but also the soil and ground flora which usually hasn’t been disturbed for hundreds of years. Once it is gone, it's lost forever, it can never be truly replaced and replicated.

“The project itself can best be described as putting a sticky plaster on the problems currently experienced on the road network. The staggering cost of the Lower Thames Crossing could have been better spent actively investigating and implementing a green travel strategy, putting infrastructure in place that enhances the environment, and our wellbeing and provides a long-term solution to the challenges we face.”

Last week, an independent report by campaign group Transport Action Network (TAN), which supports more sustainable transport infrastructure, described the project as a “dinosaur scheme from another era that should be extinct”.

It said traffic levels at the Dartford Crossing would return to existing levels just five years after the new crossing opens.

Its founder Chris Todd said: “It’s a myth debunked 30 years ago that road building grows the economy and eases congestion. Not only is the previous Conservative government’s roads programme unaffordable but even a cursory look at its own traffic projections shows congestion will worsen even if all the new roads were built.”

The sentiment was echoed by the Campaign for Better Transport group’s Michael Solomon Williams. He said: “Spending £9 billion on a road that can’t even carry a bus is utterly nonsensical and if approved by the Transport Secretary would completely undermine the government’s net-zero commitments.

“Building new roads doesn’t cut congestion, it does the opposite. Investing in public transport and rail freight is the best way to cut congestion, free up road space and grow the economy for only a fraction of the cost.”