Thousands of NHS workers are set to lose their jobs within a year through the abolition of primary care trusts, union leaders have claimed.
The government had previously announced that the job losses would happen within two years as part of its shake-up of the NHS, but Unison said the jobs will now be axed by next April.
The union said around 3,300 jobs will be lost in London alone.
Hundreds of PCT employees in parts of London including Haringey, Islington, Enfield and Barnet have now been told they will be put on 90-day statutory consultation on redundancy, according to unions.
Chris Remington, Unison's head of health for London, said: "The health white paper paves the way for massive job losses as primary care trusts are abolished. In London alone 3,300 jobs are set to go and these losses are being changed from two years into one.
"This will cause widespread disturbance to health service provision in the capital as commissioning expertise will be lost and there is no system in place to replace it."
Last week, the RCN described the government's promise that the NHS would be protected from cuts as an "urban myth" and warned that almost 27,000 jobs were facing the axe.
The RCN added that the public should be "really concerned" about the impact of the cuts and warned that waiting lists for operations would begin to rise as job losses mounted.
Dr Peter Carter, Chief Executive of the RCN, said job losses were occurring by "stealth", with trusts withholding evidence of redundancies and recruitment freezes.