David Cairns, the openly gay Labour MP for Inverclyde, has been taken into intensive care after falling ill with acute pancreatitis.
Mr Cairns, who was a Scotland Office minister under Tony Blair and Gordon Brown, has been admitted to the intensive care unit at University College Hospital, London, a spokesman confirmed.
The MPs is openly gay and is the chairman of the All Party Parliamentary Group on HIV and AIDS.
Mr Cairns is a former Roman Catholic priest and was therefore barred from election to the Commons under two 19th century laws. In May 2001, the House of Commons (Removal of Clergy Disqualification) Bill was passed.
Mr Cairns was elected as MP for Greenock and Inverclyde a month later. He was a minister between 2005 and 2008 when he dramatically resigned from Gordon Brown’s government.
He voted in favour of gay adoption, civil partnerships and the abolition of Section 28.
A Scottish Labour spokesman said that Paisley and Renfrewshire North MP Jim Sheridan would cover for Mr Cairn’s constituency business while he was in hospital.