The SNP has won the Glasgow East by-election with a 22.54% swing from Labour. Here is some of the reaction to the result:
JOHN MASON, SNP MP FOR GLASGOW EAST
"Labour MPs across Scotland will be quaking in their boots. The east end has sent a powerful message - a message that is right now resonating in Downing Street."
MARGARET CURRAN, LABOUR CANDIDATE
"While I regret losing this election and I understand that loss, I do not regret standing because for me, fundamentally, Labour is a cause and not a career - and it is a cause I will continue to pursue."
ANNABEL GOLDIE, SCOTTISH TORY LEADER
"Labour is mired in failure. Throughout the UK it is the Conservatives who are setting the political agenda."
MICHAEL MOORE, ACTING SCOTTISH LIB DEM LEADER
"The people of Glasgow East have delivered a crushing vote of no confidence in the prime minister and his Labour Government in Westminster. They have shown decisively that nobody knows what Labour stands for anymore."
ANGUS ROBERTSON, SNP WESTMINSTER LEADER
"This is an absolutely remarkable result, it's Labour's third-safest seat - rock-solid territory. Now it's over. People have had enough and Gordon Brown had better listen because at the next Westminster election the SNP is coming."
DAVID CAIRNS, SCOTLAND OFFICE MINISTER
"I said before we began that I did not think the fate of prime ministers hinges on one by-election and that whatever the outcome tonight, Gordon Brown would continue to lead the Labour Party into the next election."
DOUGLAS ALEXANDER, INTERNATIONAL DEVELOPMENT SECRETARY
"We will, of course, reflect long and hard on the result and try to understand the message that has been sent by the voters of Glasgow East."
NICOLA STURGEON, SNP DEPUTY LEADER
"Yes, it was a vote against Gordon Brown, it was a catastrophe for Gordon Brown, but it was also a positive vote for the SNP and our government in Holyrood."
DES BROWNE, UK DEFENCE SECRETARY AND SCOTTISH SECRETARY
"People do not think that the steps we are taking at the moment are adequately responding to the circumstances that they feel."
DAVID CAMERON, TORY LEADER
"I think the Prime Minister should have his holiday but then I think we need an election. I think we need change in this country, and that's how change should come about."
NIGEL GRIFFITHS, LABOUR MP FOR EDINBURGH SOUTH
"I think we have to make sure we are addressing the problems that people feel, the pain of higher petrol prices, higher food prices - all these events."
GORDON BROWN, UK PRIME MINISTER
"My full focus is on taking people through these difficult times."
GRAHAM STRINGER, LABOUR MP FOR MANCHESTER BLACKLEY
"We need a new start and that can only come from a debate around the leadership. I hope those discussions will take place."