Nick Clegg has emerged the winner after the first live televised debate between the UK's three biggest parties, according to snap polls.

A YouGov poll said the Lib Dem leader had come out on top, 22 points ahead of David Cameron on 29 per cent, with Mr Brown trailing on 19 per cent. In a second poll carried out by ComRes, Mr Clegg was again rated the victor, with 43 per cent saying he performed best, against 26 per cent for Mr Cameron and 20 per cent for Mr Brown.

There were sharp exchanges on issues ranging from crime to defence, immigration, MPs' expenses and health in what was billed as The First Election Debate on ITV1.

Summing up his appeal to voters at the end of the debate, Mr Brown said Britain did not want to repeat the "mistakes of the 1980s" when unemployment continued to rise for years after a recession.

Mr Cameron accused Mr Brown of "repeated attempts to frighten you about a Conservative government" and insisted that his party had "incredibly exciting and optimistic plans for the future of our country".

Mr Clegg repeatedly attempted to remind voters that this year's election was not a straight choice between just Labour and Conservatives, saying: "There is an alternative to the two old parties" and claiming his party offered "something new and something different".