The watchdog is recommending that the airport operator should have to sell two of either Heathrow, Gatwick and Stansted airports in the South East.

It also believes BAA should not be allowed to continue to own airports in both Glasgow and Edinburgh.

In a statement it said: "The Competition Commission has provisionally found that there are competition problems at each of BAA's seven UK airports (Heathrow, Gatwick, Stansted and Southampton in England, and Edinburgh, Glasgow and Aberdeen in Scotland) with adverse consequences for passengers and airlines."

"A principal cause is their common ownership by BAA. There are also competition problems arising from the planning system, aspects of government policy and the system of regulation.

"The CC is now seeking views on which two of BAA's three London airports should be sold and similarly which of Edinburgh or Glasgow airports should be sold."

Today BAA bosses said they had "no intention" of selling Heathrow, the authority's largest airport.

The spokesman also said that lack of runway capacity, particularly in the south is the cause of many passenger frustrations.

The commission's document is a preliminary report. The final recommendations will be published in April 2009 following a public consultation.