Campaigning: Surge in popularity no bubble about to burst, say Lib Dems

The Lib Dems' Treasury spokesman said the party was "not getting carried away" despite topping some opinion polls after Nick Clegg's success in the first televised debate between the three party leaders but said he was not surprised by the surge in support.

And he accused Justice Secretary Jack Straw of "scaremongering" and being "ridiculous" for claiming crime would rise if the Lib Dems imposed their proposal to give offenders community punishment rather than short-term prison sentences.

Yesterday the star of the Lib Dem show travelled to York Outer – a new constituency where the party is neck and neck with the Tories – before moving on to Harrogate and Knaresborough, which it already holds, to meet small business owners in a toy shop.

He was also reunited with a childhood friend he used to play with in York more than 50 years ago as he won a warm reception from shopkeepers.

Meanwhile Mr Clegg, with whom Mr Cable has denied having any rivalry, turned his focus to foreign affairs saying the "special relationship" between Britain and the United States was over and saying the UK's leaders needed to end their "slavish" devotion to Washington.

Mr Clegg, who was also forced to defend his expenses claims during a press conference, warned against "sabre rattling" over Iran's nuclear ambitions and repeated his pledge to offer a referendum on the UK's continued membership of the European Union.

Speaking outside The Rocking Horse traditional toy shop in Harrogate's Westminster Arcade, Mr Cable said: "We're optimistic we will keep this going, but we're realistic."

And he added: "We were prepared for the fact when people heard Nick and when they heard our messages and policies people would respond very positively to that but we're not getting carried away, we've got our feet very firmly on the ground."

Mr Cable insisted the party was also prepared for its policies to be closely scrutinised and insisted the manifesto was "properly costed", despite opponents questioning their proposals for a 17bn plan to raise the income tax thresholds and the Tories claiming only a vote for them will guarantee change.

With the second leaders' debate – on foreign policy – taking place tomorrow, Labour and the Tories have been seeking to undermine Lib Dem policies and Mr Clegg is under increased pressure after his resounding victory last week on domestic policy.

The rise of the Lib Dems – to top some opinion polls this week and force Labour into third in others – has rattled the other parties and led to a mixed response, with some Labour figures stressing common ground ahead of a possible hung parliament and Mr Straw going on the offensive.

Mr Cable dismissed the Justice Secretary's attack as "absolutely ridiculous", adding: "If they're saying we're not concerned about law and order they're scaremongering."

The Lib Dems are facing a fierce challenge for the Harrogate seat from the Tory candidate Andrew Jones, with Claire Kelley standing in place of retiring MP Phil Willis.

During yesterday's visit Mr Cable met Jacqueline Giles, with whom he used to play as a child in York and last saw in the 1950s, while he discussed how shopkeepers were faring in the recession.

Darren Scothern, owner of comic shop Destination Venus who said he would vote Lib Dem, revealed he has lost thousands of pounds this week because imports from America had not been arriving due to the grounding of flights.

Also on the election trail in Yorkshire yesterday was Labour's higher education Minister David Lammy campaigning with Jamie Hanley in Pudsey.

Defence move in expenses row

Nick Clegg was forced to defend claiming thousands of pounds in

expenses on his Sheffield home given his vow to clean up politics.

At a London Press conference the Liberal Democrat leader was questioned about claims including a new kitchen, gardening work to prune apple and plum trees, a new garden wall and a shopping trip to Ikea for items including cushions.

Mr Clegg, who also had to repay the cost of international phone calls claimed in error, said his constituency home was in a state of "complete disrepair" when he bought it and said he had only used the allowance to keep a "modest" home.

He regarded it as a home on loan to him from the taxpayer and when it was sold every penny of value gained would be returned.