The organisation created to champion public health appears to be too close to the Government after its head said it would prove "too controversial" to criticise Government policy, MPs have said.
A Commons Health Committee report into Public Health England (PHE) said the body - created under the NHS reforms - had not yet found its voice and was not showing independence.
Evidence received by MPs found that staff working at PHE felt they did not have freedom to contradict Government policy.
Furthermore, there appears to be an agreement whereby the Department of Health "checks" PHE reports before they are released to the press or public.
The report said: " In oral evidence, the committee asked PHE to outline Government policies which may be damaging to the nation's public health by increasing health inequalities.
"In response (PHE chief executive) Duncan Selbie said that at this stage of PHE's development it would be too controversial to directly address this question.
"The committee is concerned that the chief executive of PHE should regard any public health issue as 'too controversial' to allow him to comment directly and believes that PHE should be able to address such matters without constraint."
Regarding a PHE report on shale gas extraction, Mr Selbie also told the committee that the report was "checked in the normal way, through consultation with other Government departments, and was published in agreement with the Department of Health."
The cross-party group of MPs said organisations, including the British Medical Association (BMA), which has staff working at PHE, had told it "that PHE staff do not have freedom to contradict Government policy."
The report went on: " The committee is concerned that there is insufficient separation between PHE and the Department of Health.
"PHE can only succeed if it is clear beyond doubt that its public statements and policy positions are not influenced by Government policy or political considerations.
"The committee believes that Public Heath England was created by Parliament to provide a fearless and independent national voice for public health in England. It does not believe that this voice has yet been sufficiently clearly heard."
In its evidence, the BMA said staff at PHE had reported that the " requirement to adhere to civil service rules and regulations" was having an "impact on their ability to do their work."
The organisation added: "Particular concerns have been raised about the ability to publicly discuss or criticise public health policies."
The Department of Health also recognised that the "operational autonomy" of PHE had been questioned, MPs said, but had insisted PHE must b e able to give " advice based firmly on the science and the evidence".
The MPs' report said: " We are concerned that there is insufficient separation between PHE and the Department of Health. The committee believes that there is an urgent need for this relationship to be clarified and for PHE to establish that it is truly independent of Government."
Committee chair, Tory MP Stephen Dorrell, said: "In April 2013 PHE was created to put public health at the heart of policy-making but we are concerned that PHE has not yet found its voice.
He added: "Tackling alcohol misuse, smoking and the crisis of obesity are fundamental to improving the nation's health, but PHE has yet to strike the right tone when addressing these issues. Its public comments have often been faltering and uncertain when they should have been clear and unequivocal."
Mr Dorrell said PHE should not look to the Department of Health or other parts of Government to "prompt its research or, still less, to authorise its findings."