The health secretary will be able to "wash his hands" of the NHS after forthcoming legislation which will take away his duty to provide a national health service, according to legal advice funded by campaigners.

The legal opinion, commissioned and paid for by members of the 38 Degrees website, justifies the widespread public concern about the government's health reforms, in spite of Andrew Lansley's assurances that he has listened and responded to criticisms, they say.

The independent legal team says the health and social reform bill removes the health secretary's responsibility for NHS provision through a "hands-off" clause designed to give autonomy to commissioning groups.

David Babbs, executive director of 38 Degrees, said one legal opinion suggested responsibility for provision would instead fall to an unknown number of "clinical commissioning groups". Babbs said: "The so-called 'hands off' clause … removes political accountability, which is the only real control voters have on the way the NHS is delivered. We won't be able to fire people on regulatory bodies or private healthcare companies when things go wrong.

"None of us voted for these fundamental changes to the NHS. They weren't in any party's manifestos, or the coalition agreement, so 38 Degrees members have clubbed together to get legal advice to convince MPs that the changes shouldn't be pushed ahead and that the public's concerns need to be taken seriously."

Dr Clare Gerada, chair of the Royal College of GPs, said the legal advice gave cause for concern: "Having seen these legal opinions, they raise serious concerns for GPs. As family doctors, we want to ensure any changes to the NHS safeguard its future and benefit patients. The advice of these legal experts brings this into question. That is worrying and the government needs to respond."

The legal opinion warns that EU and domestic competition rules, which apply to business, will now apply to decisions about who provides healthcare and the running of the NHS. It says the new structure will work to the advantage of private health companies that have experience of complex procurement processes and legal teams that can challenge decisions.

A second lawyer, Rebecca Haynes of Monkton Chambers, said: "The complexity of the regime and the administrative burden in complying with the rules (which are constantly evolving through a rapidly expanding body of case law) cannot be underestimated … The relative ease with which bidders can bring claims in the high court at any stage of the procurement has led to an increased appetite for litigation and administrative challenge."

A Department of Health spokeswoman said the health secretary's responsibility for "promoting a comprehensive health service" will not change. She added: "The bill does not change current UK or EU competition legislation or procurement legislation or the areas to which they apply."

• This article was amended on 30 August 2011. The original said Dr Clare Gerada was the president of the Royal College of GPs. This has been corrected to chair.