A coalition of 20 business leaders has written an open-letter to the Chancellor urging him to approve plans for a new Lower Thames Crossing.

They say companies remain “loud, clear and unified in support of a new crossing at Location C, east of Gravesend”.

It is hoped the plans to build a new tunnel linking Kent and Essex will relieve 15% of the 135,000 cars a day that use the Dartford Crossing. It is set to carry 77,000 vehicles daily in its opening year, increasing to 89,000 by 2041.

The letter’s signatories include Eurotunnel, Tunbridge Wells-based Freight Transport Association, Kent Developers Group, the Port of Dover and Ebbsfleet Development Corporation – the body masterplanning Kent’s new garden city.

It comes after Chris Grayling, the transport secretary, told a committee of MPs last month that a final decision on a new Lower Thames Crossing would be made “very soon”.

“We have large investment decisions pending the outcome of this crucial project and we are concerned that a prolonged decision will cause uncertainty in a fragile, but growing economy...” - Letter to the Chancellor from 20 business leaders

Earlier this week, Prime Minister Theresa May told the House of Commons the announcement would be made "in due course".

The letter says public expenditure needs to catch up with private sector development in the South East, with 10% annual growth in freight traffic prompting investment in ports across Kent and Essex and the Channel Tunnel.

It says: “The Channel, London and Medway port operations account for in excess of a quarter of the UK’s GDP in trade.

“That trade, combined with other business traffic, currently flows through the highly unreliable Dartford crossings, which suffer from over 300 standstill delays per annum.

“The Department for Transport estimates traffic through this international business corridor will grow by 41% over the next 20 years.

"It is imperative that we have high-quality infrastructure to help alleviate this bottleneck to maintain fluidity and allow us to boost trade and compete with the Continent.”

The letter adds: “We have large investment decisions pending the outcome of this crucial project and we are concerned that a prolonged decision will cause uncertainty in a fragile, but growing economy.”

The proposal to build a new tunnel has been met with strong opposition from local residents on both sides of the Thames, with 47,000 people taking part in a consultation on the plans earlier this year.

The letter has been dismissed by Gravesham council, which is opposed to Option C. It described the consultation on the proposals as “deeply flawed” for failing to include details on a possible new bridge next to the Dartford Crossing, known as Option A.

Gravesham council leader Cllr John Cubitt said people in north Kent had been “sold a pup” with the argument that Option C would solve Dartford’s pollution and congestion problems.

He said: “Option A would potentially alleviate Dartford’s problems of pollution and congestion as well as taking M25 traffic out of the equation.

“But rather than make the case, [the letter signatories] have simply supported the clamour fuelled by KCC and their acolytes – like Kent and Medway Enterprise Partnership and the South East London Enterprise Partnership.

“We absolutely support a solution being found for the pollution and congestion at Dartford, but better options rather than Option C are available.”

The council has sent its own technical appraisal to Mr Grayling, which it said “draws attention to the shortcomings in the advice he is being given by Highways England”.

Mr Cubitt added: “There is a real risk that Option C would create a situation where the A2 grinds to a halt in both directions between the two crossings and problems for hauliers and private motorists will be worsened.

“There also are massive environmental implications. The loss of communities in Chalk, Shorne and beyond would devastate the green belt and dissect villages.”

The letter to the Chancellor was signed by:

Christian Brodie, chairman, South East Local Enterprise Partnership

Chris Lewis, chief executive, DP World London Gateway

Tim Cleary, director, Claridon Group

Paul Spooner, interim chief executive, Ebbsfleet Development Corporation

Jo James, chief executive, Kent Invicta Chamber of Commerce

David Wells, chief executive, Freight Transport Association

Nick Kay, development director, St Modwen Properties plc

Tim Waggott, chief executive, Port of Dover

Colin Stanbridge, chief executive, London Chamber of Commerce and Industry

Perry Glading, chief operating officer, Port of Tilbury

Denise Rossiter, chief executive, Essex Chamber of Commerce

Marc Myers, general manager, intu Lakeside

Robin Mortimer, chief executive, Port of London Authority

Glyn Jones, chief executive, London Southend Airport

Jacques Gounon, chairman and chief executive, Eurotunnel

Nick Fenton, chairman, Kent Developers Group

Ian Cochrane, managing director, Navigator Terminals

Keith Brelsford, partner, Glenny LLP

Andrew Yeardley, development director, Cogent Land LLP

Richard Burnett, chief executive, Road Haulage Association