BAA has said it is raising £400 million from shareholders

Airports operator BAA has said it is raising £400 million from shareholders amid concerns over its plans to refinance £10 billion in debts.

The group - majority owned by Spanish infrastructure firm Ferrovial - said it had "not yet finalised certain aspects" of the refinancing due to "challenging market conditions".

BAA had been hoping to transfer around £4.7 billion in bonds into a new ring-fenced funding vehicle backed by its three London airports - Heathrow, Gatwick and Stansted - as well as the Heathrow Express.

But the company said it had not yet received sufficient commitments from banks for the refinancing move.

It hopes to begin consultation with its bondholders "in the coming weeks" through the Association of British Insurers when aspects of the refinancing had been finalised.

But it also warned: "BAA may not ultimately be in such a position owing to continuing challenging market conditions."

A BAA spokesman said the company was sticking to its original timetable of refinancing its debts in the summer and denied the £400 million from shareholders was emergency funding. The group has committed financing until 2011.

BAA also owns airports in Southampton, Aberdeen, Edinburgh and Glasgow.

The group has been criticised by airlines for its monopoly in the South East and last month the Competition Commission said its ownership of seven UK airports "may not be serving well the interests of either airlines or passengers".