The government has been accused of dithering over the future plans for the A12, as concerns widen that it may cancel the project.

Council leaders and MPs from across the county have called on the government to honour plans to widen the A12 between Chelmsford (junction 19) and the A120 (junction 25) from two to three lanes in each direction.

The plan, which has been given planning approval, will also see improvements to Junctions 19 and 25, as well as the removal of Junctions 20a, 20b and 23, the movement of Junctions 21, 22 and 24, and the construction of two new bypasses.

But the government has yet to commit to funding the programme, which is expected to cost in the region of £1.2billion, arguing the country's finances are in a worse state than previously acknowledged.

Ms Patel, one of 11 co-signatories to a letter urging the government to commit to funding, said in a social media post: "The A12 widening scheme is vital to the future of Essex and East Anglia.

"It will enable economic growth and investment as well as improve safety and reduce congestion.

"I am delighted that it has cross-party support from MPs and council leaders from across the region, but this dreadful Labour Government are dithering and refusing to commit to fund and deliver the scheme.

"I will continue to campaign for the A12 to be widened and hold Labour to account."

The letter, also co-signed by other MPs and council leaders, including Essex County Council leader Kevin Bentley and veteran Tory MPs Sr Bernard Jenkin and Maldon's MP Sir John Whittingdale, argues the A12 already suffers from significant congestion and safety issues with all the key junctions being at or above capacity and combined with poor journey time reliability this has a major impact on the economy.

They said: "Without the additional capacity provided by the widening scheme the A12 will have an increasingly constraining impact on local housing and economic growth – in fact within north Essex it is the biggest immediate constraint to being able to plan more strategically – and be entirely contrary to the government's planning agenda."

They also say that given the recently proposed planning reforms, it is certain that housing targets along the A12 corridor will increase over the next 20 years by over 42 per cent across the four local planning authorities of Maldon, Chelmsford, Braintree and Colchester.

They say that "recent uncertainty" on the A12 scheme is "jeopardising the viability" of the Chelmsford Garden Community scheme, of which 6,500 homes of the total 10,000 planned are being planned on the basis the road scheme will progress.

They write: "In the event that the A12 scheme does not progress, the ability of the development to meet the garden city principles could be seriously impacted.

"At best we will lose crucial local support due to a loss of investment in critical infrastructure, and at worst the development may not come forward at all."

They also say a new 'link road' between Maldon Road and the A12 at junction 21 to bypass the Duke of Wellington junction in Hatfield Peverel indirectly supporting thousands of new homes is only possible if the widening scheme goes ahead.

The letter concludes: "We appreciate that the government has difficult decisions to make about which projects to progress

"We firmly believe the A12 widening scheme is needed to ensure government and regional strategic growth ambitions are aligned and we cannot overstate the negative implications cancelling the project would have for Essex and the wider region for decades to come."

In response, the government referred to a statement made by transport secretary Louise Haigh in July.

She said: "The financial inheritance this government has received is extremely challenging. The previous administration has left a £22 billion public spending gap this year alone – £2.9bn of which is unfunded transport commitments. Communities up and down the country have been given hope for new transport infrastructure, with no plans or funds to deliver them.

"This Government will not make that mistake. This Government will rebuild our economic foundations whilst restoring transparency and public trust.

"In recent weeks, the gap between promised schemes and the money available to deliver them has been made clear to me. There has been a lack of openness with the public about the status of schemes – some of which were cancelled or paused by the previous government, without proper communication to the public.

"As the Chancellor informed parliament, I am commissioning an internal review of DfT's capital spend portfolio. We will bring in external expertise and move quickly to make recommendations about current and future schemes.

"This review will support the development of our new long-term strategy for transport, developing a modern and integrated network with people at its heart, and ensuring that transport infrastructure can be delivered efficiently and on time.

"I am determined that we build the transport infrastructure to drive economic growth and opportunity in every part of the country and to deliver value for money for taxpayers. That ambition requires a fundamental reset to how we approach capital projects – with public trust, industry confidence and government integrity at its heart."