The government's repeated pledges to protect frontline NHS services

have been dramatically undermined by a wave of job losses at two

hospitals, with fears that as many as 1,000 posts could disappear.

Five hundred staff are to go at St George's Hospital in south London,

according to the health union Unison, which claimed that its

negotiators who have been discussing the hospital's need to save £55m

in 2011-2012 with its management had been told that shedding so many

personnel was part of that plan. The cost-saving will also lead to the

closure of three wards, with the loss of 100 beds, Unison added.

The hospital, which said it was "not immune to the financial

challenges currently facing the wider NHS", admitted it needed to

shrink its workforce in order to help it cope with the financial

challenges it is facing. It has identified 200 posts "so far" that

will go but is hoping to avoid compulsory redundancies through

redeployment of staff, it added.

Meanwhile Kingston Hospital in south-west London announced that it was

losing 500 staff, almost 20% of its total workforce, over the next

five years.

In an email to staff, its chief executive, Kate Grimes, said two key government health policies had forced the decision and warned that its action would soon be repeated by others.

Job losses are mounting across the NHS as hospitals in England struggle to cope with a £20bn efficiency drive and decisions by the coalition to restrict budget increases to 0.1% a year and reduce the fees hospitals receive for treating patients. Doctors' leaders warned that the loss of 986 jobs at the two London hospitals would prove to be "the tip of the iceberg".

A spokeswoman for the British Medical Association said: "The BMA is extremely concerned to hear about clinical job losses in England. This undermines the myth that the NHS has been protected from the financial crisis.

"Despite the continuing claims of real-terms increases for the NHS, the reality on the ground is very different. The scale of the financial challenge facing the service is such that this is likely to be the tip of the iceberg."

Peter Carter, chief executive of the Royal College of Nursing, said: "There is no way on earth the loss of almost 1,000 posts will not affect frontline care for patients. The gulf between the rhetoric of protecting the frontline and what is actually happening in hospital wards and community services is widening by the day."

The job losses in the capital take the total of NHS jobs earmarked to disappear since 1 January to at least 3,053, with another 360 personnel put at risk of redundancy, according to research by the RCN, seen by the Guardian.

The research details 18 separate cases of job losses or other cutbacks announced or confirmed in that period. Ashford and St Peter's hospitals in Middlesex and Surrey are shedding 440 posts, as is the North Lincolnshire and Gole NHS foundation trust. Southend University hospital NHS foundation trust is losing 400 jobs and closing six wards.

In Croydon, the NHS trust is scrapping 12 elective surgery beds at its local hospital, while NHS Oldham has recently closed a 28-bed community recovery unit, leaving 15 staff at risk of redundancy.

Last month Barts hospital in central London announced it was shedding 630 jobs, including 250 nurses.

The job losses put fresh pressure on the health secretary, Andrew Lansley, who is already under attack for imposing radical structural changes to the NHS in England. He and David Cameron have regularly claimed that the NHS would escape the clampdown on public spending.

According to the Health Service Journal Lansley has made the first significant U-turn on his plans by changing his mind about allowing hospitals to undercut each other in the prices they charge for treating patients.

Labour accused the prime minister of failing to honour pledges to increase the NHS budget and ensure frontline care did not suffer. John Healey, the shadow health secretary, said: "David Cameron promised to protect the NHS but cuts on this scale will hit patient care, and there's a big risk that we will now see the NHS go backwards. After big improvements in the NHS with Labour, people are starting to find waiting times rise, operations postponed and services cut back."

The £1.8bn needed for Lansley's NHS shakeup could fund almost 15,000 nurses for the next three years, Healey said.

The Conservatives in opposition promised real-terms increases in the NHS budget. Ministers say they are giving the service a 0.1% annual increase every year from now until 2015. But independent experts, such as the Nuffield Trust thinktank, say the budget will actually fall by 0.5% over that period.

Simon Burns, the NHS minister, said: "The £20bn efficiency challenge was set out by the last Labour government in 2009. Unlike Labour, who planned to cut the NHS budget, the coalition government will ensure that every penny saved will be invested back into patient services. So while it is for local trusts to determine their specific workforce needs, we have been clear that money saved must be put back into improving care for patients."

Katherine Murphy, chief executive of the Patients Association, said: "If this pattern of job cuts is played out across the country, we are deeply troubled by the risks patients may have to risk by going into hospital. Steps must be taken to stop this vicious spiral and not allow patient safety to be compromised by understaffed hospitals and wards."

• This article was amended on 18 February 2011. The original stated that St George's Hospital had announced that 500 personnel, including nurses and consultants, are to lose their jobs. That statement was made by Unison and has been corrected.