The NHS in England has finally started cutting its workforce from the record numbers now employed - the first sign of the huge squeeze to come on NHS staffing.

Figures released by the NHS Information Centre show that the hospital and community health sectors employed 3,400 fewer people in April - down 0.3 per cent from the record 1,220,000 employed in March.

The health department also drew attention to a 2.5 per cent fall of 1,150 in the number of managers and senior managers employed.

But with hospital chief executives saying privately that staff cuts of up to 20 per cent are likely over the next few years, the service also cut doctor and nurse numbers by 1,600, or 0.3 per cent.

Until now, despite the requirement for £15bn to £20bn of efficiency savings over the next few years, NHS numbers have continued to rise. The numbers, while preliminary, are the first step towards the 45 per cent reduction in management costs that Andrew Lansley has promised as he undertakes the biggest structural upheaval in NHS history.

Amid worries that NHS commissioning staff will bail out to join the GP consortia that are set to take over the purchasing of patients' care - or the private sector consortia that are likely to support them - Clare Chapman, NHS director-general for workforce, said it was "vital" that the reduction in management costs still allowed the NHS to "retain the skills necessary to deliver a better health service".

The King's Fund health think-tank said that some £6bn of the savings needed will come from the planned public sector pay freeze, the likelihood of no further reductions in waiting times, and what looks likely to be an end to the drive to provide more single hospital rooms. More could come from reducing big variations in length of stay in hospital, time spent there before operations, and by cutting out errors and reducing readmission rates, the fund said.

The big risk is that the structural changes will divert attention from the productivity drive, with that turning at worst into a programme of "cutting budgets, reducing services and sacking staff", rather than efficiency gains, said Chris Ham, the fund's chief executive.

Adrian Fawcett, chief executive of General Healthcare, Britain's biggest private hospital group, will call for the private sector to be given "a guaranteed proportion" of NHS surgery to allow it to invest in new capacity.

He will also use a conference run by the think-tank Reform to repeat calls for tax relief on private health insurance and for patients to be allowed to top up their NHS care privately.

He will also call on the government to ensure that identical information on everything from the results of treatment to waiting times are published for all health providers - public, private or voluntary.