The chairman of Esat Telecom, Mr Denis O'Brien, is close to signing a deal to purchase the property of the prestigious Quinta do Lago leisure complex in the Algarve region of Portugal in a "personal capacity" for about £25 million, The Irish Times has learned.

Mr O'Brien, who is one of the State's wealthiest businessmen, has been negotiating to buy the property for some months and is understood to have been prepared to outbid two other interested parties, one of them Portuguese.

The reported purchase price of the property would represent about a quarter of Mr O'Brien's personal wealth, which comes from his large shareholdings in Esat Telecom (the majority shareholder in Esat Digifone) and various radio stations, including Dublin's 98 FM.

A spokeswoman for Mr O'Brien confirmed last night that he was currently negotiating the final details of a contract for the property. The property contains four 18hole golf courses, stables, a five-star hotel, a large number of luxury villas and several lakes offering sailing and windsurfing. Mr O'Brien, who travels to Portugal regularly, will become the owner of the property, but will not in effect own the golf courses, which are already leased to a number of international companies for 99 years.

It is understood that Mr O'Brien will be entitled to a percentage of the green fees from the courses and will be the landlord to most of the rented property on the complex. He will also be in a position to generate income by selling some of the luxury villas and plots of land which are scattered around the perimeter of the golf courses.

The complex sometimes hosts special sporting events, often staged in front of celebrity audiences. Mr O'Brien will have the opportunity to generate revenue from this source when the sale is finally agreed. Another source suggested Mr O'Brien might consider building a second hotel within the complex.

The Irish building firm, McInerney, was involved in building the Four Seasons hotel on the site.

However, the spokeswoman for Mr O'Brien said the purchase "is strictly a property deal" and Mr O'Brien does not intend to become involved in the management of the complex. He is purchasing the property from a company called Planal which is controlled by the British Thompson family. According to sources, Mr O'Brien believes the property will significantly appreciate in value in the coming years as demand for luxury golfing facilities in the region grows. There have been several owners of the property before him.

The complex is used by many of Portugal's senior politicians and many wealthy tourists rent out villas for the summer. It is situated about 15 to 20 miles outside Faro Airport and lies within the Nature Park of Ria Formosa, which is home to many rare birds.

According to the official brochure, "the houses vary in style, reflecting the personal tastes of the owners, a gently curved villa may be followed by a classic-style mansion".

The four golf courses cover an area of 600 acres and account for 30 per cent of the golf courses in the Algarve. One of the courses, San Lorenzo, was recently voted second best European golf course in a leading golfing magazine and has hosted the Portuguese Open.