TBI, owner of Belfast International Airport, has urged its shareholders to reject an "inadequate" £517 million sterling (€837 million) hostile bid for the group from the French company Vinci.

The British regional airport operator yesterday presented its defence document which accused Vinci of trying to acquire the firm "on the cheap", and said its directors and members of their families, who hold 19 per cent of TBI, do not intend to accept the bid.

In its defence, TBI said its management team had followed a clearly-focused strategy of owning and operating airports. It emphasised its track record of acquiring eight airports in six years and its airport management and service contracts at a further 22 airports.

TBI also owns Cardiff Airport and is a majority shareholder in Luton Airport; it also controls airports at Orlando's second airport, Skavsta in Stockholm and Bolivia's three main airports.

It appealed to its shareholders to "stay on board" because its strategy is taking off.

"Vinci realises that the acquisition of your shares at 90 pence would be fantastic from their perspective. This bid is entirely opportunistic and represents a significant discount to the average prices paid per passenger in recent UK airport transactions.

"Do not sell your business for a paltry 11.7 per cent premium to the average TBI share price since we acquired Luton," the company said. It confirmed it had received expressions of interests as a result of Vinci's hostile bid and was considering them.

In its formal offer document, Vinci claimed its 90p per share cash bid offered shareholders a degree of certainty over what it described as the TBI management's "record of disappointments".

The French group said these included TBI's dependence on the UK market and its disposal of overseas interests, primarily in Australia and Costa Rica. Vinci also referred to TBI's three profit warnings in the last 18 months as further evidence to support its bid.

According to Mr Keith Brooks, TBI chief executive, the Vinci bid fails to recognise the British group's potential. "You can do the arithmetic for yourself - we are making very good profits, we have great potential and we know that our assets are scarce. This offer does not reflect shareholder value." He played down the long-term effects of BMI's switch to Belfast City Airport. TBI has warned that the loss of BMI wipes £6 million sterling off its profits.