Concerns over time it takes for health organisations to investigate fatal attacks by mental health patients have not been addressed in the first detailed guidance on the subject.

The National Patient Safety Agency guidance is aimed at improving and standardising the approach to independent investigations into serious patient safety incidents in mental health services.

Investigations should be commissioned by strategic health authorities every time a patient who has been seen by services in the past six months is found to have killed someone.

An exclusive last August revealed it regularly took five years for failings to be put right following murders or manslaughters by mental health patients.

There was no official guidance for how quickly independent investigations should be set up or for the length of time mental health trusts had to implement action plans arising from such investigations, found.

Neither of these issues is addressed in the NPSA guidance.

Michael Howlett, director of the Zito Trust, set up in 1994 to help families of people killed by mental health patients, said this was worrying.

He had hoped the guidance would place a duty on SHAs to invite investigation panels to trusts to check recommendations had been carried out.

The new guidance does confirm that mental health trusts should conduct an initial service management review within 72 hours of an incident, followed by an internal trust investigation within 90 days.

NPSA head of mental health and learning disabilities Ben Thomas said: "If we found that recommendations aren't being properly implemented or taking a really long time [to be carried out] we'd need to look into that."