Critics have renewed their attacks on the government's overhaul of the NHS in England as Parliament prepares to debate the reworked plans.
The Health Bill is due to be discussed by MPs over the next two days after ministers made a series of concessions at the start of the summer.
But groups, representing doctors, managers and academics, have still not given their full backing to the plans.
Ministers accused critics of "ludicrous scaremongering".
Nonetheless, the level of opposition still represents a major challenge in the government's attempts to keep its plans on track.
In June the government announced a series of changes to the original proposals in the face of mounting opposition.
These included giving health professionals other than GPs more power over how NHS funds are spent as well as watering down the role of competition.
'End of the NHS'
Ministers had always been prepared for a fresh wave of criticism once the bill returned to Parliament.
But the levels of disquiet coupled with the interest being shown in the changes by the House of Lords means further concessions are likely.
Much of the new criticism focused on the continued role of the private sector, the risk of increased bureaucracy and what to do with failing parts of the NHS.
Unions have continued to be the most vocal about competition.
Christina McAnea, head of health at Unison, said the bill in its current form would lead to the "end of the NHS".
British Medical Association chairman Dr Hamish Meldrum said there continued to be an "inappropriate and misguided reliance on market forces to shape services" which had the "potential to destabilise" the NHS.
Dr Meldrum also spelt out similar concerns in a letter to The Times, which was signed by the Royal College of GPs and Royal College of Nurses as well.
Even the King's Fund, a think tank largely sympathetic to the government's attempts to encourage greater competition, said there was still a worrying lack of clarity on the issue.
Meanwhile, the NHS Confederation, which represents health managers, said the amendments meant that the changes were at risk of creating even greater bureaucracy.
"There is a real danger that the NHS could find itself in paralysis," Mike Farrar, the group's chief executive, added.
Labour promised it would use the next two days to keep up pressure on the government, while some Lib Dem MPs are also expected to express concern about the plans.
Shadow health secretary John Healey said it was "still a bad bill".
He also complained that the government appeared to be rushing it through the House of Commons.
He said there were over 1,000 amendments that had to be looked at in just two days of debate.
But Labour peer Baroness Thornton said the House of Lords was geared up to scrutinise the bill in "great detail" later in the autumn.
She said there was even talk of a special committee being set up to look at the legislation, which could delay it even further.
"We have a lot of medics and clinicians. There is a lot of expertise that have a view on this," she said.
But Health Secretary Andrew Lansley said: "Claims that we aim to privatise the NHS amount to nothing more than ludicrous scaremongering.
"The reality is that we're giving more power and choice to patients over how they get treated, keeping waiting times low and cutting bureaucracy so more cash gets to the front line."