Aer Rianta is raising its stake in Birmingham Airport to 48.25 per cent from the 40 per cent it currently holds with NatWest at a cost believed to be £2 million (€2.54 million). NatWest's equity partnership division, Bridgepoint Capital, is also thought to be investing about £2 million in the deal.

The State-owned airports company and its partner are purchasing four per cent of the Birmingham operation from John Laing Investments Ltd and 4.25 per cent from National Car Parks Ltd.

Aer Rianta would be interested in acquiring the 49 per cent stake in the airport held by seven West Midlands district councils, a spokesman said. But there was no indication that this was for sale, he added.

The airport, which is managed as a public-private partnership, is the fifth-largest in Britain. It handled some seven million passengers in 1999.

The remaining 2.75 per cent of the airport is held by an employee share ownership trust.

Aer Rianta and NatWest spent £42 million on the 40 per cent stake in Birmingham airport in February 1997, it is believed.

Aer Rianta is also seeking to buy a two per cent stake of Hamburg Airport, with an option on an additional 8 eight per cent.

The company is making the bid in partnership with Hochtief, a German firm with which it already co-owns Dusseldorf Airport. It is not known, however, when the proposed deal is likely to be concluded.

Aer Rianta has also expressed interest in acquiring 41.33 per cent of Turin Airport, which is worth more than £50 million.

The company is awaiting Government approval for a partial flotation, although a number of Cabinet members are believed to be opposed to the proposal.