The retired CID man, who blew the whistle on Special Branch's running of killer agents in the Mount Vernon UVF, was told late on Friday.

Last night Mr Brown said there were still killer agents working for the PSNI.

And he accused Mrs O'Loan's team of treating him like a "terrorist thug" .

Mr Brown was informed via his solicitor late on Friday that he would not face charges arising out of a report sent by the Ombudsman to the Public Prosecution Service. The Ombudsman's office contacted his solicitor immediately after being informed by the PPS of the decision.

It is understood other ex-officers got similar news on Friday.

Mr Brown said he was accused by the O'Loan team of misconduct in public office and of conspiracy to pervert the course of justice. He said the allegations were absurd and there was never any evidence to back up the Ombudsman's case against him.

As a CID officer Mr Brown supervised the handling of small-time criminal Mark Haddock as an informer from 1985 until 1991, when he was taken over by Special Branch.

Mr Brown has previously described how Haddock cried like a baby and confessed to the 1993 sectarian killing of Sharon McKenna.

However, he said Haddock was not prosecuted because he was a protected Branch agent before he went on to take life after life as leader of the notorious Mount Vernon UVF.

He added: "We could have brought charges within a week to 10 days. We were denied clearance, denied assistance and not allowed to do our duty."

Mr Brown said the Ombudsman's office tried to have him prosecuted for failing to caution and arrest Haddock after he confessed to being the second gunman in the McKenna murder.

But he said there was no requirement for him to arrest Haddock at that point and the case was taken out of his hands by Special Branch.

"I had nowhere to go in the constabulary to complain. Perverse decisions were being made but I couldn't do anything about them," he said.

Mr Brown was arrested by the Police Ombudsman's office as he arrived at Belfast International Airport following a family holiday last August. He is furious over his treatment.

"The manner of my arrest was totally unnecessary," he said. " I was arrested at the airport like some terrorist thug.

"I can not impress enough the trauma my family has been put through.

"It has been worse than living under terrorist threat, worse even that the trauma of the bomb attack on our home by the UFF.

"How dare Mrs O'Loan treat me in this way. It has been unbelievable," said Mr Brown.

He also said there are still killers working as agents inside the PSNI.

Mr Brown added: "I'm not saying Sir Hugh Orde knows this. But I'm saying there are still some agents who are killers."