A new body set up to help the NHS learn from mistakes will "struggle to gain trust" unless it is given an independent legal footing, experts have said.
The Healthcare Safety Investigation Branch (HSIB) needs its independence written into law so NHS organisations, workers and the public can have confidence it is not "part of the regulatory establishment", according to an article in a medical journal.
The HSIB for England came into force last April with the aim of supporting and guiding hospitals on investigations and carrying out some probes itself.
It was initially formed as an independent body under the auspices of the regulator NHS Improvement.
But the editorial, published in the Journal of the Royal Society of Medicine, says legislation is needed to ensure the HSIB is independent.
"It is imperative that primary legislation is brought forward to establish Healthcare Safety Investigation Branch on an independent institutional footing," wrote experts from the University of Oxford.
"Without this, the Branch will have to work unnecessarily hard to combat the perception that it remains part of the regulatory establishment, meaning it may struggle to gain the professional trust, public confidence and authoritative view that its work depends upon."
They argue that it is "hard to overstate the critical importance of independence".
Co-author Charles Vincent said: "Safety issues span the entire healthcare system, so the HSIB must be able to impartially investigate all organisations entirely free from conflict to build an authoritative system-wide view."
The paper also argues that the success of the body "depends on trust".
Lead author Carl Macrae added: "To encourage the open flow of safety information, healthcare professionals and organisations must be assured that any information generated solely for the purposes of safety investigation – such as witness statements or investigators' notes – will only be used for the purposes of learning and will not be routinely passed to regulators or courts."
The Government has already committed to establishing a "safe spaces".
Health Secretary Jeremy Hunt has previously said the creation of these "safe spaces" for staff to speak about what went wrong without fear of repercussion would help bring new openness to the NHS.