There are fears that long-awaited work on a notorious stretch of the A417 could be delayed as the Government faces a near-£1billion funding gap in their road investment plans.
Concerns have been raised over whether construction on the notorious Air Balloon bypass – a scheme dubbed the A417 'Missing Link' - will now take place in 2021 as planned.
A report by the National Audit Office reveals ministers face an £841million hole in funding for the Government's £11billion road building project – which was set to cover 112 upgrades in five years from April 2015
According to last year's report, 16 upgrades to motorways or A-roads could be shelved or face significant redesign and 19 projects could be delayed to after 2020.
But the Conservatives say the A417 is not linked to any of the projects mentioned in the report and have accused the Lib Dems of electioneering.
Councillor Paul Hodgkinson, leader of the Liberal Democrats on Gloucestershire County Council, (Bourton & Northleach), said: "The 'Missing Link' has been a problem for Gloucestershire for more than 20 years. It is often very heavily congested seeing up to 45,000 vehicles a day and there are frequent tragic accidents with more than 340 casualties in the past 15 years.
"The National Audit Office is also stating that 19 projects could be delayed until after 2020 - this may include the A417 'Missing Link' or mean it goes further down the queue of projects.
"It is extremely worrying and once again throws up lots of uncertainty as to whether this stretch of road will ever be fixed."
A public consultation is set to be launched for a road-building scheme to propose a solution to the 'Missing Link' by 2018.
Richard Ford, chairman of Gloucestershire UKIP, said the report shows the national roads project was "just a cosmetic exercise by the Conservative/Lib Dem coalition in order to try and win extra votes."
He said: "It is ironic that this information should now come to light ahead of the 2017 General Election. I very much hope that the voters of Gloucester and elsewhere in Gloucestershire will remember when they go to the polls on 8th June that the Conservatives' manifesto commitments are worthless, just as this 2015 manifesto commitment has proved to be."
The Green Party, however, has said building bigger and more roads has resulted in air pollution and congestion.
Sarah Lunnon, Stroud Central councillor for the Green Party, said: "We do not need a motorway, a M417 across the Cotswolds, we do need a transport system that works for people and our economy.
"It's time to stop using solutions that have continually failed - an immediate and relatively cheap solution to many of the A417 problems would be the use of fixed speed cameras to even out traffic speeds and flows at junctions.
"This would have the added benefit of reducing noise and air pollution without scaring our countryside. The cost could have been met by the funds Gloucestershire County Council have already ploughed into a scheme that would see the Cotswold become a link road between the Midlands and London. Is that what we want for our county?"
The NAO report scrutinises the Government's Roads Investment Strategy, which runs until 2020 – which the Conservatives say does not include the A417 Missing Link.
Councillor Nigel Moor, the council's cabinet member for infrastructure (C, Stow-on-the-Wold), said: "The A417 isn't remotely connected to these projects, the Liberal Democrats know that, and are just making things up in advance of the elections. Thanks to the Conservatives, the project to fix the A417 Missing Link is moving ahead on schedule."
Councillor Mark Hawthorne, leader of Gloucestershire County Council (C, Quedgeley), added: "For years a key stumbling block to sorting the A417 was the Lib Dem MP for Cheltenham, who refused to back the plan. The Lib Dems have some cheek to complain about slow progress that they caused themselves.
"The only risk to the project I see is if Martin Horwood is somehow re-elected and goes back to blocking this vital scheme."
The Department for Transport said it is considering the findings of the report.
A spokesman for the department said: "This government is taking the big decisions for Britain's future, and we are investing a record £15 billion on road schemes which will cut congestion, speed up journeys, and boost the economy across the country.
"As this report acknowledges, we have made significant progress in managing our major roads more efficiently, and we are confident Highways England will deliver safe and reliable roads that deliver value for money for the taxpayer."