NHS safety organisation must be independent, say MPs.

A new organisation designed to make the NHS in England safer must have its independence guaranteed in law, a committee of MPs says.

The Healthcare Safety Investigation Branch (HSIB), which has a £3.6m budget, will carry out about 30 reviews a year. It is based within NHS Improvement, the body that overseas NHS Trusts.

The MPs also call for a single public inquiry into historical cases of avoidable harm in the health service.

It is hoped that the new body will enable NHS staff, patients and their families raise awareness about serious risks to safe care, and allow hospitals and other providers to learn from mistakes.

The cross-party Public Administration and Constitutional Affairs Committee (PACAC) which has examined the work of the new body, claims that HSIB will fail without new legislation.

Committee chairman, Bernard Jenkin MP, said: "We have consistently called for primary legislation to make HSIB fully independent, and create a credible 'safe space' which will enable the NHS to properly learn from past mistakes.

"The secretary of state's decision to set HSIB up as an NHS quango was disappointing. A secure legislative base would enable HSIB to emulate the successful air, marine and rail investigation branches. Were the present non-statutory arrangement to be permanent, it would be an intolerable compromise."

Scandals at Mid Staffs and Southern Health Trust have highlighted failings in how the NHS responds to patients' complaints and deaths.

The MPs say the HSIB should be "an exemplar of high-quality clinical investigations" with local NHS providers still carrying out the bulk of inquiries.

On the need for a single public inquiry to review historical cases of failings in the health service, the MPs say: "This should be seen in the context of other wide-reaching inquiries, such as the public inquiry into historic child sexual abuse, the Hillsborough disaster inquiry and the Savile inquiry into Bloody Sunday.

"A single public inquiry would provide closure to those affected by patient safety incidents, which cannot otherwise be obtained."

Patient safety campaigners at the charity Action against Medical Accidents (AvMA) questioned whether the no-blame approach was the right one.

Chief executive Peter Walsh said: "We believe that both PACAC and the government are wrong to prioritise the creation of a so-called 'safe space' for health professionals above guaranteeing openness and honesty with patients or their families about their own treatment.

"This would undermine public confidence in HSIB and run against the principle of the newly-created duty of candour.

"We do want to see protection of staff who do the right thing, but most health professionals would agree that denying patients access to the truth is no way to do that."