Police in Northern Ireland have reached agreement on sharing information with the Police Ombudsman after shortcomings in a probe linked to a notorious loyalist mass murder.

The ombudsman's office said the deal will allow for better searching for and sharing of information.

The PSNI failed to produce all its files on the Sean Graham Bookmakers killings in Belfast in 1992 to the watchdog's investigation.

Ombudsman Marie Anderson said: "I know that providing us with information has at times been difficult for police, not least because of the vastness of the task but also the legal duty on all of us to protect the most sensitive of information.

"But the public must have confidence that police provide my office with all the information it asks for.

"Both the chief constable and I agree such disclosure is central to confidence in both our organisations."

She came into office last year wanting to develop the process to ensure her investigators had the best access to material.

Ms Anderson said: "From the beginning I wanted to become more directly involved and get a detailed understanding of how police search their vast estate for material.

"I soon came to the realisation that my investigators needed to be involved at every stage of that search on occasions."

Five people were killed by UDA paramilitaries in the bookmakers gun attack.

The Criminal Justice Inspectorate previously said no specific guidance was available to PSNI officers searching for material for a Police Ombudsman probe into how the murders were investigated.

In February last year, the former ombudsman said investigators had identified sensitive PSNI material that had not been made available in relation to the Sean Graham killings.

The PSNI acknowledged disclosure failings, apologised to those affected, and said that it had not sought to deliberately withhold information.

Chief Constable Simon Byrne said the signing of the memorandum of understanding followed much hard work and commitment from staff in both organisations.

He added: "The Ombudsman and I firmly agree that the effective disclosure of information is central to public confidence in both our organisations, particularly in relation to dealing with the past.

"I welcome this agreement and believe it will support the searching and sharing of information as well as the legal duty on all of us to protect sensitive information."