The stretch of road will link the M74 and the M8

Friends of the Earth Scotland said �180m had been allocated for the compulsory purchase of property.

It also said the cost of creating a job through the project was �100,000, compared to �2,000 per job spent by Scottish Enterprise last year.

But the Scottish Executive accused the campaigners of being too simplistic.

FoE Scotland divided the project's overall budget of up to �500m by the number of jobs that could be created and said it came to �100,000 per job.

It is very bad value for money Duncan McLaren FoE Scotland

Chief executive Duncan McLaren said its estimate was based on figures given to the public inquiry into the project.

"That concluded that at best the scheme would generate 5,000 additional jobs for Scotland as a whole," he said.

He described the executive's suggestion that 20,000 jobs would be created as "exaggerated and simplistic" and said this had been rejected by the public inquiry.

"It is very bad value for money," he said.

Economic benefits

Ministers gave the scheme the go-ahead after overruling the recommendation of the public inquiry.

The executive said campaigners were overlooking the wider economic benefits of the scheme, such as easing congestion and improving the competitiveness of the west of Scotland, and said it could actually create 20,000 jobs.

The campaigners also said the extension would put about 3,000 jobs at risk, through the displacement or closure of businesses.