Amanda McMillan says the Government money that funds the rail link to Prestwick must be scrapped as it benefits Ryanair, the airport’s main carrier, at the expense of other airlines.

Ms McMillan also says the Scottish Government must restore the air route development fund and do more to support all of Scotland’s airports as they compete against other European countries that are being given greater protection by their governments.

She says cash-strapped ministers could divert money saved from supporting Prestwick’s rail line to the development fund. Currently, the terms of the ScotRail franchise set by the Government means passengers who have an air ticket to Prestwick receive a discount.

Glasgow Airport is owned by Britian’s biggest airport operators, Spanish-owned BAA, while Prestwick is owned by Infratil Airports Europe.

Writing in The Herald today, Ms McMillan predicts a bright future for Glasgow Airport including a multi-million-pound boost to be announced in the near future.

However, she warns that the air route development fund, which was scrapped two years ago, must be restored if Scotland is not to be left behind other European countries including small ones such as Cyprus.

She says: “Scotland must act quickly if it is to stand any chance of competing in Europe. Scottish ministers tell us there is no money. Why not start by scrapping the public subsidy, through ScotRail, of the Prestwick Airport rail link? This unfair and anti-competitive subsidy provides free or discounted fares for anyone travelling with ScotRail to Prestwick.

Ms McMillan’s call for the reintroduction of the route development fund was supported by Graeme Sweenie, Prestwick’s chief commercial officer. He said it would be a “significant catalyst in bringing new routes and visitors to Scotland”.

He added: “However, I am disappointed that Amanda should criticise our rail link. At a time when Scotland is struggling to attract visitors, the last thing we want to do is make it difficult for them to get to their onward destinations.”

The re-introduction of an air route development fund was also supported by Labour transport spokesman Charlie Gordon, who called for investment in Scotland’s airports. “Scotland deserves a 21st-century transport network,” he said.

A Scottish Government spokesperson said: “ScotRail is required to offer discounts for train transport to Prestwick Airport for those with a flight booking to encourage use of rail to access flights, particularly for new routes. Any change to this arrangement would run counter to Government policy to encourage passengers to make greater use of sustainable transport.”