Jack Tasker probed the 29stone politician’s warped lusts – and believes he was a major supplier of boys to other sex beasts.
And retired Jack says Smith’s name even came up during inquiries by fellow officers into killings linked to a notorious gay brothel.
But Jack, 82, says his own investigations were shut down by police top brass – and he was told he’d be “back in uniform” if he didn’t leave Smith alone.
The former detective sergeant, who served with Lancashire Police for 35 years, said he has no doubt there was a cover-up to protect Smith’s depraved antics.
Jack said: “Smith’s name even cropped up in talks with colleagues as a possible suspect for a murder at the Elm Guest House in London, where we knew Cyril was a regular visitor.
“It is all being investigated again now.
“It was always my impression that he was a supplier, as well as being a full-blown paedophile.
“I believe he was supplying kids for a lot of powerful people.”
Jack also revealed for the first time that Smith had unsupervised access to a young offenders’ centre in his Rochdale constituency.
He said: “Smith was a regular visitor to Buckley Hall Detention Centre, which was full of boys.
“He used to come and go as he pleased.
“People who worked there told me he had his own set of keys – not to the perimeter but to the interior.
“He used to come in, pick his keys up and wander around alone.
“He was allowed access to anywhere inside and could have anything he wanted.”
Last month, the Metropolitan Police confirmed they were investigating possible historical murders linked to a paedophile ring centred on Westminster officials.
The group are also linked to Elm Guest House, a hotel in Barnes, south-west London, which was run as a gay brothel in the 1970s and 80s.
Disgraced Smith was one of the high-profile names said to have attended orgies there.
But Jack had investigated Smith even before then, leading a major investigation into the then-councillor dating back as far as 1969.
“I think we would have cracked him but officials would not allow us to go there again”
He said: “We saw eight young lads who had been his victims but Smith eventually found out.
“We later discovered that his mother worked at the police station as a cleaner.
“She cleaned the stairs and offices and heard all the gossip.”
Jack interviewed Smith, with the politician “sweating profusely” and stumbling over his answers.
Jack said: “I think we would have cracked him but officials would not allow us to go there again.
“What really did me was what those lads must have thought.
“That was the bit that stuck in my craw.
“We were ordered to stop.
“We were visited by a superintendent and a chief superintendent.
“They were from the Lancashire Police HQ at Hutton.”
He said the officers forced him to unlock a drawer containing files on Smith.
“They told me to take everything out that relates to this case and added ‘We mean everything, every scrap of paper and every note you’ve ever made’.
“They said we would be back in uniform if anything went wrong.”
He added: “I would still like to see justice done.
“I thought we had let these victims down.”
Jack said files he produced and others from a subsequent inquiry ended up “languishing in a Special Branch safe at Hutton for years”.
It was there they were finally discovered by Special Branch detective Tony Robinson.
We told last week how Tony, now 81, had been threatened by former colleagues at Lancashire Police over speaking to the press about what he saw.
Now we can reveal that Tony has contacted MP Simon Danczuk, Labour member for Cyril Smith’s old Rochdale seat and has named the police officers who he says warned him off.