Plans for a major shake-up of local health bodies in England are "ill thought out" and likely to adversely affect patient care, MPs have warned.
Primary care trusts commission 80% of NHS services
The radical reorganisation of primary care trusts, which control 80% of the NHS budget, would be hugely disruptive, the Commons health committee argued.
There was no case for halving the number of PCTs and cutting the number of health authorities, it added.
But Health Secretary Patricia Hewitt said the changes would save £250m.
She said the plans, which would cut the number of PCTs from about 300 to between 70 and 130, and reduce the number of strategic health authorities from 28 to nine, were a response to local wishes.
The committee said the initial consultation process over PCTs was "insufficient and flawed".
Mrs Hewitt added: "Stronger and more effective primary care trusts will mean reduced management and administrative costs.
"This means that all over the country, primary care trusts will be able to decide with their clinicians how this extra money can be used to improve local services for patients."
The government also hoped the shake-up would boost PCTs' role on commissioning services.
However, the committee said the costs of the major shake-up "outweighed the benefits" and urged the Department of Health to more carefully consider the impact of its plans on staff.
Destabilising effects were already becoming apparent, with reports of staff leaving because of uncertainty over their roles, the MPs said.
The committee found it took an average of 18 months for organisations to recover from major restructuring and a further 18 months for benefits of any changes to emerge.
But the shake-up was happening only three years after existing PCTs were set up.
"Just as the benefits of PCTs (established in 2002) are about to be realised, the government has decided to restructure them."
The committee concluded: "The cycle of perpetual change is ill-judged and not conducive to the successful provision and improvement of health services.
"Major restructuring should only be undertaken if there is an overwhelming argument in its favour - in this case there is not."
Dr Gill Morgan, chief executive of the NHS Confederation which represents health service bodies, said the report delivered a timely warning that a 'cycle of perpetual change' in the NHS could derail improvements in health services.
But the confederation agreed with the direction of travel of the government's proposals, she said.
She added: "The NHS has shown remarkable resilience to cope with 23 major reorganisations since 1974 and we are confident that PCTs will ensure patient care is not damaged by this latest restructuring."
Dr Mike Dixon, Chairman of the NHS Alliance which represents PCTs, said there had been problems with communication and the implementation of the reforms, but said they had gone too far to be ended now.
"We have got to get on with it so we know where we stand - the worst thing would be to stay in limbo land," he said.
But he agreed with the committee that there needed to be a full debate about future private sector provision of healthcare heralded in by the PCT shake-up.
The committee directed stinging criticism at plans to contract out or privatise some services, which it said could lead to fragmentation of community services and make "joined-up care" even harder to provide.
While trusts will no longer be forced to contract out services, the committee said it was appalled by the lack of clarity on who will provide them in the future.
As the report was published public sector union Unison released the results of a poll suggesting 71% of Labour MPs opposed PCTs concentrating solely on commissioning.
The union's general secretary Dave Prentis said: "It's a disgrace that health visitors, community midwives, occupational therapists, district nurses - the backbone of our local community services - are threatened with transfer to the private sector.
"Booted out and left to the vagaries of the market."