Airports operator BAA has so far racked up £15 million in defence costs fighting off an £8.75 billion hostile takeover approach from a consortium led by Spanish support services group Ferrovial - and expects the final bill in the heated bid battle to be "significantly" higher.

The owner of Heathrow and Gatwick airports has retained City banks UBS and Rothschild as advisers on its defence against Ferrovial, which first kicked off its bid interest in the early part of February before going formal with a hostile offer in the middle of last month.

BAA said today that it had drafted in UBS and Rothschild before the formal bid came in - and that bid-related costs to the end of March had reached £15 million.

Rothschild is BAA's existing adviser but UBS was brought in after a beauty parade in early February.

Today's disclosure on costs does not take account of dealing with Ferrovial's official hostile proposal, or contending with another preliminary approach for BAA that came from infrastructure funds led by Goldman Sachs.

"The total costs to the company of this ongoing situation are, at this stage of the process, uncertain but will be significantly greater than £15 million," BAA said this morning.

The heavy cost of defending itself emerged as BAA disclosed it had bumped up revenues for the financial year to the end of March by 7.4 per cent to more than £2.2 billion.

But, although operating profits rose 8.1 per cent to £710 million, hefty exceptional costs mainly related to property valuations, saw pre-tax profits slide 17.3 per cent to £757 million.

Pre-tax profits before exceptionals were up 2 per cent to £620 million.

Mike Clasper, BAA's chief executive, is forecasting a rise of 3.5 per cent in passenger numbers at the seven airports it operates, which also include Stansted, during the course of this year.

Last year passenger numbers rose 2 per cent to 144.6 million, below a similar initial 3.5 per cent forecast last year.

But Mr Clasper hailed its achievements for the year, which came despite the impact of the London July bombings and the impact of the damaging British Airways dispute with caterer Gate Gourmet.

"These results are a reminder of BAA's core strengths that enable us to consistently generate shareholder value; a unique portfolio in a dynamic sector; strong growth of our London airports; even stronger returns from our other businesses; and a first-rate management team creating value," Mr Clasper said.

Shares in BAA added 1p to 837p, valuing the airports operator at more than £9 billion.

For full details on the shares click here

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