BAA intends to fight a call to sell off any further airports after the Competition Commission last month provisionally ruled the group must sell three of its seven locations, including two in London and either Edinburgh or Glasgow.

Colin Matthews, chief executive of BAA, said improvements had to be made and acknowledged concerns users might have about BAA's monopoly of Scotland's biggest airports, but defended the company's record at Edinburgh, Glasgow and Aberdeen.

"I am sure there are a whole range of opinions in Scotland," Matthews told The Scotsman. "We are, I hope justifiably, proud of the performance of BAA in the Scottish airports. Of course we need to improve customer service. That is a healthy state of mind for an operator to have."

Matthews denied that putting Gatwick up for sale was designed to quell the commission's case against BAA, saying the competition issues were "fundamentally the same whether we are selling Gatwick or not".

"It is possible we won't be successful, but in any event understanding the breadth of public opinion and conviction that there needs to be a change is something we take seriously," he added.

But Ryanair boss Michael O'Leary said the sale was "just the latest attempt by the BAA monopoly to get itself off the hook of the Competition Commission's recommendations" and called for the government to force the sale of Stansted and a Scottish airport.

"Airlines and passengers have been abused for many years with high prices and abysmal service at all of the BAA's London and Scottish airports and the 'trick' of selling off Gatwick won't end this abusive monopoly," he said.

News that Gatwick was up for sale drew immediate interest from Sir Richard Branson's airline Virgin Atlantic which said it would "relish the opportunity to bid for Gatwick as part of a consortium". Other potential bidders include German builder Hochtief, which said it was "considering getting involved".

A spokesman for Manchester Airports Group said it would look at a possible bid if it added value for shareholders, while an industry source said it was "logical" that Global Infrastructure Partners (GIP), the consortium that owns London City airport, would also look at a deal.

Some estimate that Gatwick, one of Europe's busiest airports, could fetch £3 billion.

Analysts at Collins Stewart, however, said that price was "unlikely" as the value of the airport's assets, as calculated by regulators, was just over £1.5bn. The analysts have a "sell" recommendation on BAA parent company Ferrovial's shares.

A BAA spokesman stressed the process was at a very early stage, and it was yet to appoint advisers or evaluate any of several expressions of interest.