Guinness is expected to brew a special anniversary stout to mark its 250th birthday next year, it emerged today.

The commemorative beverage may be launched in a blaze of worldwide publicity around St Patrick's Day in March.

The 250th anniversary marks the date which founder Arthur Guinness signed the lease on his famous St James' Gate brewery in Dublin - in December 1759.

The facility is now one of Ireland's biggest tourist attractions, drawing hundreds of thousands of visitors each year.

A spokesperson for Guinness parent company, Diageo, declined to comment on events planned for the 250th year but industry sources insist the anniversary brew will form a major part of celebrations.

Arthur Guinness opened his first brewery in Leixlip, Co Kildare, in 1756 before moving to St James' Gate in Dublin three years later.

A new 500 million euro (£474 million) brewery in Leixlip is expected to produce one billion pints a year when it becomes operational in 2013.

Guinness heir and owner of Leixlip Castle, Desmond Guinness believes the black stuff is now firmly part of the Irish identity, more than two centuries after it was founded.

"I drink wine myself but I suppose you could say Guinness has become a staple of the Irish diet in many ways," the historian said.

"It was even regarded as medicinal. It used to be given free to nursing mothers in hospitals and to people who gave blood."

Mr Guinness, 76, remembers the 200th anniversary celebrations of Guinness in 1959.

"The clan may very well come together. We're scattered all over the world so a reunion would be something," he explained.

Sales of Guinness stout are bucking the general beer trend by increasing by more than 2% in the 12 months to the end of June.

The number of pints of the black stuff sold also rose by 6% internationally with Nigeria, Cameroon and Ghana among the strongest markets.