A British police chief investigating more than 200 murders during the Troubles has said he will publish an interim report on his findings before the end of next year.

The statement is a clear shot across the bows to the British government, which has indicated that it plans to ban prosecutions and investigations into killings during the conflict in Northern Ireland.

Operation Kenova was established five years ago to investigate more than 50 murders linked to a man believed to be the British army's most high ranking agent within the IRA, code named Stakeknife.

Freddie Scappaticci, from west Belfast, has always denied being that agent. He now lives in an undisclosed location outside Northern Ireland.

Jon Boutcher, who leads the investigation, said his interim report will be published before the end of next year and will focus on the activities of the Provisional IRA, police, British military and their agents and informers.

"In particular the report will focus on the organisation that committed these awful murders, state intervention or otherwise, and whether steps were, or were not, taken before serious criminal conduct was carried out or subsequent to it to prevent a full investigation," he said in a statement.

"At the very outset of Kenova I made a promise to all the affected families that I would produce a public-facing report outlining our findings to give them the truth of what happened to their loved ones, including who was involved and in what capacity.

"After five years, and with more than 30 files with the Public Prosecution Service of Northern Ireland for consideration, we are now in a position to start preparing for the interim report's release. The report's content will hold great importance to all of those who were involved."

Operation Kenova has invited those with an interest in the investigation to have their say on the plans to publish the report.

Mr Boutcher wants to agree a "protocol" setting out the parameters of the report.

"I am acutely conscious that different stakeholders with different persepectives are concerned that our reports will say either too much, or too little," he explained.

"The aim of the protocol is to ensure that we do neither. I am committed to finalising and reporting the truth openly and transparently without fear or favour towards any party. I simply need to find a process which will allow me to do this fairly and lawfully."

Mr Boutcher has made it clear that he opposes the planned ban on prosecutions and investigations into Troubles killings.

The former chief constable of Bedfordshire Police has also said he will go public if the British government or military establishment attempts to curtail his ongoing investigation.

In July, the Kenova team said he had uncovered new forensic evidence it believes could identify the killers of Co Louth farmer Tom Oliver, a father of seven shot dead by the IRA in 1991.