Greater Manchester Police have been accused of attempting to silence a young officer after he found Cyril Smith at the home of a known sex offender with two drunk underage boys.

The officer, now retired, claims he was told "in no uncertain terms" not to mention that he saw the alleged paedophile MP at the home of a sex offender, who had spent half his life in jail. Also present were two young boys, one of whom was a runaway from a children's home.

The officer, who had only been in the job for six months, said he was threatened with the Official Secrets Act after he found Smith at the address in Stockport following reports the occupier had been committing lewd acts.

When he arrived, the Rochdale MP was there with the pensioner along with a police officer in civilian clothes.

The officer, who wished to remain anonymous, told the Manchester Evening News: "I had been in the force about six months. The occupier was about 70 and seemed an old grandad type. In the house was Cyril Smith and a police sergeant in civilian clothes. The officer identified himself and showed his warrant card, saying he was there "on other business".

"There seemed to be a party going on, with two young lads there. Smith and the officer left. The boys, aged about 14 to 15, were drunk.

"One was missing from a children's home. I called for a van and took him back. The other lad walked off. The old man was arrested and I took him to the main police station in Stockport."

The following day, the officer was called to a meeting with a senior officer and mentoring officer, Don Mackintosh, who would later be convicted for being a paedophile. The officer was warned he would break the Official Secrets Act if he told anyone about the incident.

The officer added the pensioner at the address only received a caution after committing the latest sex offence, a decision he described as "very strange".

The claims emerged after the Independent Police Complaints Commission said it was investigating 14 claims of corruption in London's Met Police force across four decades, including one claim an investigation into a paedophile ring involving Smith was dropped shortly after he was arrested.

GMP described the allegations as "concerning" and said they will be investigating.

Assistant Chief Constable Ian Wiggett said: "These fresh allegations will now be examined by Operation Clifton, a criminal investigation launched by GMP in July 2014 into how previous reports of child sexual abuse were handled or allegedly covered up.

"Clearly there are people who are willing to talk to the media but have not yet spoken to police. We have spoken to the Manchester Evening News about these latest allegations and we have asked them to pass our details to their source with the reassurance we will treat the information they give us in the upmost confidence.

"These allegations are concerning and will be treated seriously. GMP has allotted considerable resources to Operation Clifton, and we are committed to investigate all the allegations as best we can.

He added: "As these new allegations relate to misconduct by police officers, even though officers may have since retired, the matters have been referred to the Independent Police Complaints Commission."