The Competition Commission is expected to back the break-up of BAA, the UK's largest airports operator, when its issues its findings imminently.

The watchdog will give recommendations for the future of BAA in a preliminary report at 0700 BST on Wednesday.

BAA, whose seven airports include Gatwick, Stansted and Heathrow, has been accused of poor service.

The commission has said BAA's ownership structure might not serve well the interests of passengers or airlines.

The chairman of BAA recently told the BBC he expected the commission to order the break-up of the company, but that such a move would not lead to effective competition against BAA's main airport Heathrow.

As well as a near-monopoly in the South East of England through its ownership of Heathrow, Gatwick and Stansted, BAA also owns Edinburgh, Glasgow, Southampton and Aberdeen airports.

The watchdog launched an enquiry into BAA following concerns that its ownership of multiple airports meant it was overstretched, and might lack the capacity to embark on several development projects simultaneously.

Next steps

If the watchdog says the current ownership model is not in the public interest then BAA could be forced to sell Gatwick and/or Stansted airports and also either Edinburgh or Glasgow airport.

It is thought that several international companies might be interested in buying different BAA airports including Manchester Airport Group and Global Infrastructure.

Other airlines have long urged BAA, which handles more than 60% of all flights arriving and leaving the UK, to be broken up.

BAA, which was acquired by Spain's Ferrovial in 2006, has faced stiff criticism for its poor customer service, most recently for its handling of the Terminal 5 opening at Heathrow.

But it has also had the burden of higher security and maintenance costs.

The commission's initial report in April said it was worried by "BAA's approach to the system of planning airport development".

On Monday, BAA said it had managed to refinance 13.3bn in debt, of which 3bn could be used for investment immediately.