Calls were growing last night for Audit Scotland to investigate a multi-million-pound expansion of air services off the west coast.

Council leaders in Argyll and Bute have expanded Oban's Connel Airfield massively, partly in the hope of winning direct flights to Glasgow. They have invested more than £6m in upgrading Connel and building tarmac runways on the islands of Coll and Colonsay.

However, with Transport Minister Tavish Scott scheduled to open Oban's new "Hebridean Hub" next month, it is becoming increasingly clear that no airline will agree to fly the route.

Ellen Morton, the Liberal Democrat councillor who leads the opposition to Argyll's ruling Independent group, said she wanted to see an inquiry into the project.

Mrs Morton said: "If people are raising legitimate concerns about the financing and funding and viability of this airport, then I think it would be useful to have a proper investigation by a body separate from the council.

"I have always been utterly opposed to the council's support for the airport at a time of terrible financial stringency."

Ardchattan Community Council, which covers Connel, earlier this month made the unusual step of calling for Audit Scotland to look into the project.

The new-look Oban Airport is supposed to launch subsidised, scheduled flights to Coll and Colonsay on August 1.

Building work, however, is behind schedule and the council has still to find an operator for the island routes, which are partly aimed at getting 15 island children home at weekends from school in Oban.

Critics last night said Argyll could have delivered lifelines to Coll and Colonsay without the need for new tarmac strips. They said that the scale of expansion ordered by councillors was needed only to pave the way for unrealistic scheduled flights to Glasgow and beyond.