Former RCGP chairman Professor Steve Field, chairman of the NHS Future Forum set up to lead the consultation, said he only accepted the post because he believed it was not just a cosmetic exercise.
Meanwhile, GP and MP Dr Sarah Wollaston (Conservative, Totnes) has warned that the government must accept significant changes to its plans to avoid a defeat for the Health Bill in the House of Lords.
However, backers of the NHS reforms have set out elements of policy they believe are non-negotiable, and said a 'major change in the direction of travel' was unlikely. A senior GP adviser to the DoH warned that GP-led commissioning and the removal of PCTs and SHAs must not be reversed.
Professor Field said the 'listening exercise' would be a series of meetings, events and other ways of hearing people's concerns about the Health Bill.
He said Mr Cameron sees the exercise as an opportunity to create a 'stronger Bill'.
'I have been guaranteed by the prime minister that this is an exercise which he supports and takes seriously and that if change is needed to the Bill then it will change,' he said.
'I have taken this on because it isn't just a cosmetic exercise.
It will be taken seriously by Downing Street and the secretary of state.'
But Dr Paul Charlson, chairman of the Conservative Medical Society, said it was likely the Bill would go ahead in its current form. 'My feeling is that the Bill is likely to go through pretty much as it is. If there are changes they will not be major ones,' he said.
DoH national clinical commissioning network lead Dr James Kingsland agreed the listening exercise would not result in a 'major change in the direction of travel'.
'This is not about starting from scratch. The government is definitely not thinking it has got it all wrong,' he said. 'It's about looking at the concerns, clarifying them and if the concerns have got real weight then they will be addressed.'
Dr Kingsland said the exercise could bring 'further clarification' around competition and Monitor's role in the NHS.
But he added that it would be 'disastrous' if the government backtracked on plans to hand GPs commissioning powers or scrapping PCTs and SHAs.
'If we lose those basic building blocks of the reforms then I don't know where we will end up. We will be adrift,' he said.
GPC deputy chairman Dr Richard Vautrey said the listening exercise must result in action and 'significant amendments' to the Bill.
Dr Vautrey said the government must now act on the detailed responses it already has from GP organisations about the reforms.
RCGP chairwoman Dr Clare Gerada said she was 'sceptical' about what the listening exercise would achieve.
'I don't think we need a listening exercise. The government needs to address the concerns around the Health Bill, not just go through another process. There is enough evidence, and enough information already.'