Macquarie Airports - the investment fund with a stake in Birmingham International Airport - has reported a 64 per cent rise in its first half underlying net profits.

The group - which has also invested in Sydney, Rome, Brussels, Copenhagen and Bristol airports - saw profits before financing costs of A$ 566.2 million (£ 238.1 million).

However, under new international financial reporting standards, it reported a fall in first half net profit of 54 per cent to A$ 157.3 million (£66.16 million) because acquisitions are no longer amortized.

MAp owns a 14.9 per cent stake in Birmingham International Airport - which it currently values at £194 million.

MAp is managed by Australian bank Macquarie - the owners of M6 Toll operators MEL.

Including MAp's stake, the group owns 24.125 per cent of Birmingham Airport, whose other owners are Irish group Aer Rianta with a similar holding, the seven West Midlands councils with 49 per cent and the Employees Shares Trust, 2.5 per cent. MAp chief executive Kerrie Mather said strong growth in underlying earnings at all airports, active capital management and the successful integration of new acquisitions, was benefiting shareholders.

"All airports are continuing to deliver strong cash flow as we expand passenger choice through increased flights and services, as well as improved offerings in retail, food and beverage, car parking, property development and other commercial initiatives," Ms Mather said.

Earlier this month Macquarie announced that it was considering a takeover bid for the London Stock Exchange.

The Australian bank said its "deliberations were at the most preliminary of stages" and any formal offer would be made through a consortium and probably in cash.

Its interest threatens to disrupt the plans of pan-European exchange Euronext, which is awaiting the final outcome of a Competition Commission inquiry into an earlier takeover approach.

Macquarie Bank typically focuses on property and infrastructure investments including Isle of Wight ferry operator Wightlink and South East Water - which supplies water to approximately 1.5 million people in the UK.

Macquarie also has a 31 per cent interest in gas distribution firm Wales & West Utilities and is the sole owner of Energy Power Resources, which owns and manages the UK's largest portfolio of biomass fuelled renewable energy assets.

Macquarie is dubbed the 'millionaires' factory' because of the big bonuses it pays. The bank operates in more than 21 countries and has over 6,500 staff.

It manages about A$91 billion (£38.7 billion) in assets worldwide, including motorways, utilities, aged care housing and property to media assets.

Macquarie began in 1969, with just three staff, as Hill Samuel Australia, wholly owned by London- based investment bank Hill Samuel. It renamed itself Macquarie Bank in 1985.

Macquarie, which has a market value of about A$14.7 billion (£6.2 billion), listed on the Australian Stock Exchange in 1996.

It has reported successive years of record profits since 1992 including a net profit of A$823 million (£350 million) for the year to the end of March.