The north-east could miss out on hundreds of millions of pounds of fishing and offshore decommissioning work if the A90 is not upgraded.
The startling revelation was made as a Scottish MEP laid out the business case for dualling the 14-mile stretch of the vital route between Ellon and Peterhead.
Thousands of cars, vans and HGVs travel on the single carriageway road every day and yesterday campaigners said that unless action was taken the region’s economy could be left crippled.
Conservative MEP Ian Duncan has urged the Scottish Government to take advantage of a European Investment Bank (EIB) loan to fund what would be a huge infrastructure project.
It is estimated that the cost of upgrading each mile of the route would be about £10million.
Mr Duncan said: “The future of the decommissioning industry is huge. It will be a multibillion-pound industry.
“A lot of that will be done in the north-east of Scotland, almost certainly Peterhead, and that will be important 10 or 20 years down the line.
“Peterhead is also becoming a green energy hub with the carbon capture proposals and I think that’s also not been taken into account.
“I’m not criticising the Scottish Government, but now is time to reconfigure and take our case to the European Union.
“There are industries such as fishing which are located in Peterhead because they need to be. But what about these new industries, why would they locate in Peterhead when the road infrastructure is terrible?”
Mr Duncan has already held talks with officials from the EIB, who are “eager” to back the scheme in the same way they did with the M8 Glasgow-Edinburgh motorway project, which was supported by a £175million loan.
The EU is open to funding applications in early 2016 and a grant could be awarded by next summer.
Mr Duncan warned: “The north-east could become Scotland’s forgotten corner.”
Last night, economist Tony Mackay said the north-east had been “badly served” by infrastructure investments in the past.
“Successive Scottish Governments have assumed that because of the oil and gas industry the region did not need additional public investment,” said Mr Mackay, of Inverness-based Mackay Consultants.
“The long-delayed Aberdeen Western Peripheral Route is a good – or bad – example of that.”
Earlier this year Transport Scotland released figures showing that every day 13,000 vehicles travel on the three-mile stretch of the A90 from Ellon to Toll of Birness
Some then branch off towards Mintlaw and Fraserburgh, but between 8,000-9,000 vehicles use the road to Peterhead.
Transport Scotland has said the investment priority in the north-east is completing the AWPR project.
A Scottish Government spokesman said: “We are addressing years of under-investment in north-east transport infrastructure with the delivery of the largest roads construction project currently under way in the UK, the AWPR and Balmedie to Tipperty project.”
The spokesman said that Transport Scotland was also redesigning one of the north-east’s “most notorious bottlenecks” – the Haudagain roundabout in Aberdeen.
The body is also undertaking an appraisal of all modes of transport, including upgrading the A90 and reintroducing the railway between Aberdeen, Peterhead and Fraserburgh.
The spokesman added: “It is important that any road, rail or other project put forward as part of this work has a strong evidence base and business case. Once this has been established appropriate funding options will be considered.”