The SNP's John Mason won 11,277 votes (43.08% of the poll), up 26% on his party's vote in the 2005 General Election. He beat Labour candidate Margaret Curran - already a Glasgow MSP - on 10,912 (41.69%) as the Labour vote fell by nearly 19%.

The result is a devastating blow to PM Gordon Brown and one of the biggest by-election upsets in political history.

The seat had been one of Labour's safest with a majority of more than 13,500, but a massive swing of over 22% saw the nationalists secure it.

If the performance was repeated at a General Election, Mr Brown himself would lose in Kirkcaldy & Cowdenbeath, and a slew of top Cabinet ministers would also be kicked out of the Commons.

The SNP, whose leader Alex Salmond had promised a "political earthquake", won with a majority of 365 on a high turnout of 42%.

The swing was just over 22% - making it the biggest by-election upset in Labour's Scottish heartlands since the loss of Glasgow Govan in 1988.

The by-election was sparked by the resignation of David Marshall on health grounds and followed hard on the heels of heavy defeats for the party in Crewe and Nantwich and Henley.

The result was delayed after Labour requested a recount of the ballots, but eventually the nationalists' margin of victory went up.

To make matters worse for Mr Brown, the Tories also put in a strong performance by leapfrogging the Lib Dems to come third.