Former Liberal Democrat leaders Charles Kennedy and Lord Steel of Aitkenhead yesterday unveiled a plaque to commemorate Sir Henry Campbell-Bannerman, the Glasgow-born Prime Minister who died 100 years ago.

Lord Steel praised his predecessor as Liberal Party leader as an "overlooked radical" whose 1906 landslide victory had paved the way for a succession of reforming governments.

"He led the way for the longest period of successful radical government ever, which was continued by Herbert Asquith and David Lloyd George," Lord Steel said.

"It was a remarkably successful government which introduced the extension of the franchise, the vision of home rule all round in the UK, the introduction of the old age pension and unemployment benefit. He gets overlooked because Asquith and Lloyd George were Prime Ministers for much longer."

The plaque was unveiled at the home in Bath Street, Glasgow. He died in 1908, three weeks after ill health forced him to resign as Prime Minister .

Mr Kennedy said: "Campbell-Bannerman is more recently going through a reappraisal. Roy Hattersley has written a biography of him and calls him one of the great radical social reforming Prime Ministers."

He is also the first Prime Minister to be known as such. His predecessors were referred to by the more formal title of First Lord of the Treasury.