London (PTI): British Prime Minister Gordon Brown on Friday suffered the biggest electoral setback since taking over office a year ago with his ruling Labour losing the Glasgow East by-election to the Scottish Nationalist Party (SNP).

Brown hails from Scotland, and Labours inability to retain what was considered a safe Scottish seat under his leadership once again sparked talk about replacing him as the party leader.

Ratings for Labour and personally for Brown have touched new lows in recent months.

John Mason of the SNP today won by 365 votes by polling 11,277 votes over Labours Margaret Curran, who polled 10,912.

The by-election was caused by the resignation of Labours David Marshall on health grounds. In the 2005 general election, Marshall had won with a majority of 13,507 in Glasgow East over the SNP.

Mason described the SNPs victory as a "political earthquake" and said voters had sent a message that Brown and his government were "out of touch" with the peoples issues.

The Labour party has suffered a series of electoral setbacks since Brown took over as prime minister from Tony Blair in June 2007.

The government has also been pinned down by policy reverses, mainly on unpopular income tax issues in recent months.

The most notable of the Labour losses were in the May local elections, the London mayoral election, and the Crew and Nantwich by-election.