Tory MP Zac Goldsmith today backed cuts at a hospital serving his London constituency - despite pledging before the election that he would resign over axed services.

The millionaire MP for Richmond Park was a frequent face at Kingston Hospital during the campaign, and was even joined by David Cameron, both vowing "to keep investing" in it.

Last April Mr Goldsmith told a hustings at Richmond Chamber of Commerce: "Kingston Hospital will be safe," and if the promise was broken "I will trigger a by-election and allow people to penalise my party."

But in a U-turn today, he said the loss of almost 500 posts, including frontline staff, was necessary. "Hospitals around the country are having to find savings, and ours is no different," he added.

"But having met and discussed the implications with the chief executive, I am absolutely confident the annual five per cent savings can be made without undermining the hospital. The team is confident the level of service will remain, and believe that in some cases it will be improved."

Geoff Martin, chairman of London Health Emergency, said: "Goldsmith joins ConDem big-hitters like Clegg and Cameron... who pledged support for Kingston Hospital before the election and are now backing savage cuts that could prove its death knell."

Shadow health secretary John Healey added: "Mr Cameron told the country before the election that he'd tell any Cabinet minister making cuts to front-line services to go away and think again. It's him who should think again about his reckless plans for the NHS."

The Prime Minister said today: "I would urge every health authority to look at what they can do in terms of saving back office costs, saving bureaucracy and trying to keep everything on the front line."

A total of 486 posts will go at Kingston in the next five years, including 22 consultants; 214 nurses, midwives and health visitors; 55 scientific and technical staff; and 140 non-clinical jobs. The hospital says the cuts are being forced on it by an expected 25 per cent reduction in its budget.

The hospital was also at the heart of Nick Clegg's election campaign. In April the Deputy Prime Minister, whose youngest child Miguel was born there, used it as a backdrop and said: "I'm going to use any power and influence to do anything I can to help the NHS, and do anything that stops anything that would threaten this maternity ward."