Sex abuser MP Cyril Smith piled pressure on police officers while they investigated his "sordid" abuse of boys.
Smith demanded police in Rochdale tell him the names of people contacted to provide witness statements in 1970.
The Liberal MP was also warned about interfering with witnesses by officers in transcripts which have now been released for the first time.
No charges were ever brought against Smith during his lifetime, despite long-standing suspicions held by police backed by evidence.
Smith, who was famous for his enormous girth, wielded considerable influence in the Lancashire town during the 1960s and '70s.
He used his contacts to confront police about the child sex abuse investigation, which could have derailed his parliamentary career before it began.
Smith was exposed as a sex abuser by allegations made public against him in November, centring on a hostel for boys he helped to establish.
The allegations against Smith emerged in the wake of Jimmy Savile scandal last year. His surviving brother Norman told IBTimes UK: "I don't understand why nobody mentioned these things until now."
Smith died in 2010, at the age of 82.
According to transcripts of Smith's conversation with officers at Rochdale Police Station, Smith told how he talked to a boy: "He told me what you had been asking him. He told me he had made a statement to you.
"I've seen two of them and the third came to see me. I've asked them if they have made statements."
Later in the conversation, Smith said: "I've got to give a decision, one way or another, whether I'm going to fight the next Parliamentary Election."
Current Rochdole MOP Simon Danczuk said the transcripts prove Smith interfered with police inquiries.
Danczuk said: "This exchange reveals how hard Cyril was pushing the police to drop charges and the fact that he was warned for interfering with witnesses shows he was clearly trying to influence the investigation.
"I know from speaking to police officers that Cyril had too much influence on the case and this transcript is a perfect illustration of what he was up to."
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