Ministers insist they remain committed to providing a rail link to Glasgow Airport and are expected to announce the next stage soon.

A Scottish Executive spokeswoman said: "Rail links to both Glasgow and Edinburgh airports are among the executive's top 10 transport priorities and ministers are committed to delivering these projects."

A report in The Herald newspaper on Wednesday claimed that consultants carrying out studies into the Glasgow link had decided that none of the four suggested routes would provide value for money.

Iain Gray, transport minister

According to the article, not enough tickets would be sold to cover the running costs.

The consultants, Sinclair Knight Merz, have however endorsed a rail link to Edinburgh Airport - even though it would cost twice as much as the Glasgow plan at �265m.

The executive spokeswoman added: "The consultants' report is being finalised and has yet to be sent to ministers. An announcement on the way forward is expected shortly."

She also pointed out that the executive had given Strathclyde Passenger Transport (SPT), which arranges rail services in the west of Scotland, �1.5m last year to put the necessary legal framework in place for the airport link.

Running costs

"This demonstrates our commitment to delivering this project for Glasgow," she added.

The Herald claimed that the confidential report, which has been prepared for transport minister Iain Gray, predicted that by 2020 up to 3.3 million people a year would be using the Edinburgh link.

By contrast, only 930,000 people would be using the Glasgow link on an annual basis.

The report said that even the best of the four Glasgow options, a quarter-hourly service from Glasgow Central station, would not cover its running costs.

Sinclair Knight Merz said the best Edinburgh option would be a �265m proposal diverting the main Edinburgh to Glasgow line through a one-mile tunnel under the airport.