The coalition's health reforms could lead to the NHS ceasing to provide key services and may make tragedies like the death of Baby P harder to prevent, leading doctors have warned.

Their analysis of the health and social care bill found the changes will result in worse care for millions of patients, with serious conditions such as cancer, wider health inequalities and poorer patients being disadvantaged.

The dramatic warnings by leading doctors are contained in an assessment by the Faculty of Public Health (FPH) of the risks involved in the forthcoming overhaul of the NHS in England.

The bill poses "significant risks … to patients and the general public" and could well damage "people's health and patients' experience of care," according to the faculty, which represents 3,300 public health specialists in the NHS, local councils and academia.

"It is likely that the most vulnerable who already suffer the worst health outcomes will be disadvantaged as a result of the enactment of the bill," the document states. Poorer people are unlikely to be able to use the greater patient choice that the bill entails, it adds.

"Operation of choice in an environment of multiple providers will disadvantage those who are less educated, have reduced access to resources such as the internet, or for other reasons are less able to navigate the healthcare market."

Whole areas of healthcare provision may disappear and patients could be forced to go private because clinical commissioning groups (CCGs) – the new groups of local GPs who will become responsible for agreeing and paying for patients' treatment from April 2013 – are only tasked with deciding what services are needed in order to "meet all necessary requirements" of the populations for whom they are responsible.

"As such, it is possible for CCGs to cease to commission services which are currently available through the NHS if they do not consider them to meet a reasonable requirement. Access to such services in the future might be available only through private healthcare," the FPH claims.

Handing GPs the right to decide what care is and is not provided "will also lead to an increase in geographical variation in service provision – the postcode lottery," and such variation may become "more overt" owing to doctors or patients lobbying CCGs.

Imposing "a competitive market" on the NHS will make it difficult to provide joined-up care for the rising number of patients with long-term conditions, as separate organisations collaborating to provide care "may be seen as anti-competitive and incur substantial financial penalties," the assessment adds.

Dr John Middleton, vice-president of the FPH, which recently joined other medical organisations in calling for the bill to be scrapped, said: "Patients with long-term conditions such as diabetes need co-ordinated care between GP, community and hospital. Under the current system they go to the primary care trust if any aspect of their care is at fault.

"Under the new system they may need to go to the NHS commissioning board for GP or optometrist care, the CCG if their hospital service or chiropody causes them a problem, Public Health England for their eye screening and the local authority public health service for their weight management and lifestyle services – it's a recipe for unco-ordinated care and everyone passing the buck. The current reorganisation is a recipe for things getting worse, not better."

The document echoes warnings about the perils of the overhaul of child health already made in some primary care trust risk registers. "Of particular concern are the risks identified around safeguarding children from abuse and neglect. The loss of designated professionals and weaknesses in information sharing between organisations poses an increased risk to the safety of children," the analysis says.

Middleton added: "After several years of relative stability, this unwelcome and unnecessary reorganisation is disrupting services and splitting apart professional relationships which are needed to protect patients and the public."

NHS arrangements for emergency planning, screening and immunisation programmes are also "unsafe" because of flaws in the bill, Middleton said.

"The FPH remains concerned at the risks to public protection in emergency planning. NHS commissioning board directors of emergency planning cover huge geographical areas: from Land's End to Dover, from Yarmouth to the Welsh border, and from Cheshire to Northumberland, and London. Each of these areas is huge and covers multiple Local Resilience Forums around which blue light services are organised, so NHS directors of emergency planning face extraordinary difficulties covering their sectors.

"Directors of public health at local authority level will 'assure' the system, but will have no powers or resources to enforce what needs to be done to make the systems safe," he said.

The FPH also warns that allowing private operators to provide more state-funded health services, together with the increased competition between NHS organisations, will increase the amount of money spent on administering the system and incentivise hospitals to treat patients needlessly.

"The market environment will increase transaction costs and lead to the loss of economies of scale as large providers could be broken up. Market incentives will lead to supplier-induced demand where hospitals perform unnecessary and potentially harmful treatments to generate income. Management costs will also increase as the new GGCs will need to buy in legal and procurement expertise to support them in fulfilling their new commissioning responsibilities", the risk assessment report states.Health minister Simon Burns said: "This report is scaremongering. The reality is if we choose to ignore the pressures on the NHS, it will face a financial crisis within a matter of years. The bill means for the first time ever there will be a duty on all parts of the health system to reduce health inequalities, and the public health budget will be ringfenced from 2013.

"Far from preventing integration, the health and social care bill will introduce legal duties to promote it throughout the health system. Failure to act will threaten the very values we hold so dear – of a comprehensive health service, available to all, free at the point of use and based on need and not the ability to pay. We will not allow that to happen."