A break-up of airports group BAA will look more likely this week following the publication of an interim report from the Competition Commission.

The commission’s “emerging thinking” is likely to question whether BAA’s ownership of the three large London airports – Heathrow, Gatwick and Stansted – restricts competition and incentives to provide capacity. It may make a similar comment on BAA’s ownership of Glasgow and Edinburgh airports.

Senior aviation industry sources say the report and the commission’s final verdict, expected later this year, could lead to BAA eventually selling one of the London airports.

Gatwick is thought to be the favourite for disposal. There is likely to be a long queue of would-be buyers, with the West Sussex airport expected to fetch around £2 billion – more if caps on its charges are scrapped at the time of the sale.

This week’s interim statement could have other ramifications for the company. A negative report might disrupt a planned multi-billion pound refinancing, which has already been delayed because of the credit crisis.

Senior BAA executives said yesterday they had no prior knowledge of this week’s findings, but said they were braced for the commission to follow the tenor of earlier reports.

“They [the commission] are headed down a pretty familiar path,” said one company source.

BAA, led by new chief executive Colin Matthews, has owned the three London and two Scottish airports since it was privatised in 1989. It also owns Southampton and Aberdeen airports.

Airlines have over the years argued vigorously, but in vain, for a break-up, saying the company’s dominance restricts the development of the industry.

The commission began its probe of BAA just over a year ago. The issue was referred to it by the Office of Fair Trading (OFT), whose own inquiry was critical of the airports group.

The OFT said that common ownership of the London airports led to a lack of incentives to investment, higher charges and costs, and that there was evidence it also contributed to poor service.

BAA has defended its position, saying it alone has the critical mass to provide the necessary investment in new runways and terminals in the southeast, noting that other proposals for development have failed to make it off the drawing board.

The company is also likely to point out that the government white paper on aviation three years ago promoted the provision of new runways – first at Stansted, then Heathrow – ahead of the multiple ownership of airports.

BAA was taken off the stock market in 2006 for £10.3 billion by a consortium of investors led by Ferrovial, the Spanish infra-structure group. It also assumed £6 billion in BAA debt.

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