A leading architect of Tony Blair's health reforms warns in the Guardian today that the NHS will not survive as a universal tax-funded service without a change of policy. Chris Ham, professor of health policy at Birmingham University, said a "fundamental weakness in the design of the reforms" made it impossible for the NHS to deliver the improvements in efficiency that will be needed when growth in its budget slows next year.

Prof Ham, director of strategy at the Department of Health from 2001 to 2004, said the government hoped to increase efficiency by making hospitals compete for NHS patients. This gave them a strong incentive to raise quality and cut costs.

But most hospital beds were occupied by patients who were admitted as emergencies - mostly older people who had no choice where the ambulance took them.

They could be kept well at home if GPs, community nurses and hospital specialists worked closely together. But Prof Ham said: "With healthcare organisations competing with each other for a bigger share of the NHS budget, there is little incentive for them to collaborate to substitute care in the community for care in hospitals."

The government had strengthened the position of foundation hospitals and private-sector treatment centres, but gave "scant attention" to building up the power of primary care trusts that buy services from them on behalf of NHS patients.

"This has created a fundamental weakness in the design of the reforms with the purchasers of care lacking the expertise and resources needed to make the healthcare market work efficiently," Prof Ham said. "The levers and incentives do not exist to reduce variations in productivity and performance on the scale needed to fund future medical advances."

His analysis reflected majority opinion among leading doctors, NHS managers and Whitehall policymakers who attended a series of private seminars at the Nuffield Trust, an influential health research institute. The seminars, chaired by Prof Ham, concluded that the government's policies are in danger of sucking more resources into hospitals and starving primary care.

He said the reforms had to be reformed to achieve a sustainable universal service and called on Gordon Brown, as chancellor and prime minister in waiting, to address the problem. The warning came as the NHS begins to prepare for the end of record growth in the health budget. Since 2002 health spending has increased by about 7% a year in real terms, but this rate of growth is due to end in March 2007.

The NHS expects its subsequent funding to keep pace with the general rate of inflation, but managers fear this will be not nearly enough to keep pace with the rising cost of drugs and increasing demand from larger numbers of older people.

Prof Ham said it was unrealistic to expect sufficient savings from eliminating waste or cutting bureaucracy. The only way of balancing the books was to change "core medical processes" by winning support from doctors and nurses for new ways of working - often outside hospital, closer to patients' homes.