Nick Clegg said voters had a "sense of malaise" and a "feeling of powerlessness", which required a more "broad-brush" approach from candidates.

He told a fringe meeting at the Lib Dem conference in Blackpool that the general election campaign had been "fairly piecemeal".

The party gained 11 MPs, below the expectations of some members.

'Cash register approach'

Mr Clegg said the Lib Dems had targeted the "grey vote", adding: "We wrote down a fairly random list of blandishments to target the elderly.

"We took a cash register approach. It was as if you pressed the right buttons and Lib Dem would come up."

But this had not worked and the party had in fact attracted younger voters, even some who might lose out with the party's policy of charging 50% income tax on earnings above �100,000.

Many voters did not analyse manifesto pledges in detail, Mr Clegg said.

Candidates must "speak their mind" on the doorstep, and show more "emotional intelligence", Mr Clegg added.

Sarah Teather, the Lib Dem local government spokeswoman, said: "If we are serious about being a party of the future, we have to be prepared to take on both the Conservatives and the Labour Party. In all seats we take votes from both."