I'm only <i>doubling</i> the size of my mansion, says Mitt Romney

Mitt Romney's holiday home is worth about £7.3m (REUTERS)

The Republican presidential hopeful Mitt Romney has interrupted earnest discussions about the US economy, healthcare and foreign policy to issue a qualified denial of news reports that he is quadrupling the size of his holiday home in California.

The former Massachusetts governor, who is often portrayed as a wealthy elitist by rivals, was visiting a roadside diner in New Hampshire when a local newspaper publisher asked him about recent coverage of building work at the $12m (£7.3m) beachside property in La Jolla, a suburb of San Diego.

Mr Romney issued a bizarre response, claiming that reports of the remodelling operation were highly exaggerated. He is not quadrupling the size of the residence, which sits on one of America's most exclusive parcels of real estate; rather, he is merely doubling his living space.

An account of the conversation was published on Monday by Joe McQuaid, of the New Hampshire Union Leader newspaper. He had wondered why Mr Romney chose to give foes "raw meat" by attempting to upgrade one of his many mansions while America teeters on the brink of recession. The would-be US President responded that it was "not accurate" to accuse him of quadrupling the dwelling's size.

"The application he made, two years ago, was to double the living space by turning one story into two," says Mr McQuaid. "The 'quadrupling' was a measurement of added non-living space, including a basement and garage."

Mr Romney's enormous wealth, between $190m and $250m, was largely made during an early career in finance. His private property portfolio includes an $8m compound on Lake Winnipesaukee in New Hampshire.

All of the other major Republican candidates are multi-millionaires, but Mr Romney, as a relative centrist, is particularly vulnerable to allegations of elitism. Despite appearing to be the most presidential figure in Republican debates so far, his position as leader in the long-running race has recently crumbled.