Airport operator BAA should sell three of its seven UK airports and two of its three in London, the Competition Commission has ruled.

The body is advising the organisation to sell two of Heathrow, Gatwick and Stansted and one of Glasgow or Edinburgh. BAA has made it clear it will not sell Heathrow.

Should both Gatwick and Stansted be sold, they should end up in the hands of different parties to promote competition, the regulator said.

"BAA has argued that there is no scope for competition to develop so long as there are capacity constraints," said Christopher Clarke, who headed the inquiry for the Competition Commission.

"We take the opposite view. Unless the market is opened up to competition, there is a serious risk that the current capacity constraints will persist."

A final decision will be taken by the regulator in April 2009.