Government claims that competition has improved quality in the NHS and saved lives are based on flawed research, experts say.
As ministers prepared to defend Andrew Lansley's controversial health reforms, which reach the House of Lords this week, academics at the University of London have attacked a key pillar of the Health and Social Care Bill.
The Cabinet and the Department of Health are also on alert to prevent a "peers revolt" that could lead to parts of the bill being referred to committee – fatally stalling the legislation.
Liberal Democrats, led by Dame Shirley Williams, were alarmed that the duty of the Secretary of State to provide a free, universal and comprehensive health service was being weakened. Ministers are expected to offer concessions to reassure them.
Fears that the bill will be a Trojan horse for the private sector are also fuelling protests. Some 2,000 demonstrators blocked Westminster Bridge yesterday during a demonstration organised by UK Uncut against "the wholesale privatisation of the NHS".
The latest criticism of the bill, by Professor Allyson Pollock of Queen Mary, University of London, and her colleagues, challenges the evidence on which the reforms are based.
Writing in The Lancet, she said a study used by the Prime Minister, David Cameron, to back the case for more competition in the NHS was littered with errors.
That study, by researchers at the London School of Economics, suggested that mortality rates for heart attack patients were lower in cases where more hospitals were within travelling distance of the patient's GP surgery.
But Professor Pollock said: "Our examination of this research reveals it to be fundamentally flawed. The paper simply doesn't prove either cause or effect between patient choice and death rates."
Among the demonstrators who took to Westminster Bridge yesterday in a rally organised by UK Uncut were trade unionists and members of the public including the comedians Josie Long and Mark Thomas.Reuse content