Obama, or as he may now be known, 'O'Bama', is a descendant of one Falmouth Kearney, who left famine-ravaged Ireland in 1850 and took a boat from Liverpool to New York.

The revelation was uncovered by the subscription genealogy site, ancestry.com.

The site includes a boarding document showing that Kearney arrived from Liverpool in New York and another document showing that he and his family later settled in Ohio.

According to the site, 19-year-old Falmouth Kearney landed in New York harbour on March 20, 1850, on board the SS Marmion.

The site does not say what country Falmouth was from, or if that is even his real first name, but his surname is commonly associated with county Mayo.

There is no further official documentation of his life until an 1860 US Federal Census, which shows that he was living in Ohio and working as a farm hand.

He lived among Irish relatives and then married, had eight children and moved to India.

Three of his daughters married three brothers with the surname Durham.

Barrack Obama's mother is a direct descendant from one of her couples and she carried Durham as a maiden name.

Like President Reagan, Clinton, Nixon and many others, discovering a previously unknown Irish ancestor should help Obama's chances of becoming president.

It could also help win over white voters reluctant to vote for a black candidate, an issue which polls show is a continuing factor in US politics.