WORK on a new £400 million bypass around Aberdeen will finally begin following a defeat in the UK's highest court for campaigners who wanted it scrapped.

The Supreme Court yesterday rejected an appeal from opponents of the road scheme which was first proposed in the years after the Second World War and approved by Scottish ministers in 2009 after a four-month public inquiry.

Supporters say it will now mean 14,000 jobs for the northeast of Scotland as construction gets under way in 2014 with the aim of opening by spring 2018.

The court unanimously dismissed William Walton's third challenge to the 28.5-mile Aberdeen Western Peripheral Route (AWPR).

Mr Walton and fellow campaigners in RoadSense now admit it looks like the end of their fight unless their lawyers can come up with a new strategy.

Aberdeenshire Council leader Jim Gifford was delighted with the decision, saying: "It marks the beginning of the delivery of the most significant piece of major infrastructure in the north-east since the discovery of oil in the North Sea in the 1960s."

First Minister Alex Salmond, the MSP for Aberdeenshire East, said: "The decision by the Supreme Court is a just ruling for the north-east of Scotland and an opportunity for Scotland that marks the end of five incredibly frustrating years for the vast majority of people who are behind this ambitious project.

"Over the next three decades, the AWPR and the Balmedie to Tipperty road schemes are expected to bring in an additional £6 billion to the local economy, creating around 14,000 new jobs. It is therefore crucial that we crack on and deliver these vital and, frankly, long overdue infrastructure projects."

The new road – which could cost more than £400m because of the hold-ups – will bypass Aberdeen by linking Stonehaven in the south to Blackdog north of the city, and is supported by the business community and drivers frustrated by congestion and delays.

However, 8000 objections, mostly on environmental grounds, forced a public inquiry in 2007. Mr Walton's case said the Scottish Government had failed to comply with European law in the breadth of the environmental assessment.

Supreme Court judge Lord Reed said: "Mr Walton's contention that the public inquiry held into the scheme was unfair under the common law ... is unanimously rejected."

However, the judges did reject the Court of Session's conclusion that Mr Walton was not an "aggrieved person" and so was ineligible to bring a court action.

Tory transport spokesman Alex Johnstone, who is a north-east MSP, said he welcomed this decision which would bring to an end "the futile opposition to this vital new road".

However, Mr Walton, a university planning lecturer, said he was surprised by the ruling. "This is not what I had hoped for, or expected," he said. "I have always maintained the route selection process was flawed."

Patrick Harvie, MSP, co-convener of the Scottish Greens, said: "Now it seems the public purse will have to cough up a staggering £400m for a system of roads that will simply encourage more traffic, contradicting Scotland's low-carbon ambitions, and doing little to reduce congestion in Aberdeen city centre."

However, Richard Baker, Scottish Labour's infrastructure spokesman and north-east MSP called for work on the bypass to begin as soon as possible.