Public health experts fear the government's plans to reform public health could be a "nightmare" that will make it harder to respond to emergencies and increase health inequalities.
They widely criticised the proposed NHS reforms and suggested the new service would be more fragmented than at present.
The vast majority also rejected one of the government's key reasons for implementing the Bill, improving care commissioning.
These views were supported by the British Medical Association (BMA) which said the plans could cause problems when planning major events such as the next year's London Olympics.
A survey of nearly 1,000 public health specialists conducted by the UK Faculty of Public Health (FPH) about the Health and Social Care Bill found that almost three-quarters (71%) of respondents disagreed or strongly disagreed that reforms would create a safer and more effective response to public health emergencies.
Even more (81%) disagreed or strongly disagreed that inequalities in healthcare access would fall, while 83% disagreed or strongly disagreed that the NHS would see less bureaucracy.
A similar number (79%) thought the reforms would lead to the fragmentation of the public health discipline with 50% strongly agreeing.
And three quarters (76%) disagreed or strongly disagreed that the reforms would lead to improved healthcare commissioning, one of the Department of Health's central reasons for introducing the legislation.
The FPH said the research produced a clear message that there is ‘significant concern about public health's future - for both the specialty itself and for the future health and wellbeing of the public'.
‘Words such as "chaos" and "nightmare" were used to describe the current and anticipated situation in the NHS and public health systems,' it added.
The BMA noted that the findings add further weight to calls for the Health and Social Care Bill to be withdrawn.
Dr Richard Jarvis, co-chair of the Public Health Committee at the BMA, said: "The Faculty's survey results echo what the BMA has been hearing from its members in the last year.
"The country is facing very serious public health problems arising from obesity, alcohol misuse and smoking.
"We need to plan for major events like the London Olympics and we need to be able to respond to threats like future pandemics. Dismantling and fragmenting the workforce that has expertise in these areas will hinder our ability to combat these complex issues.
"We call on the government to shelve the plans now before serious harm is done to our capability to meet the most important public health challenges in England," he added.