A man who accused Leon Brittan of sex abuse has admitted having an interest in "witch-hunts" against Conservative politicians, according to reports.
The Times said Chris Fay, a former social worker, had drawn up a list of VIP paedophile suspects in the 1990s including the former home secretary.
The paper quoted the 69 year old, from south London, as saying he had been a "very left-wing Labour councillor" and was "right up for witch-hunts against right-wing Tories".
It comes after MP Tom Watson said it was his "duty" to notify the Director of Public Prosecutions (DPP) about allegations made against the late Lord Brittan after facing calls for him to apologise.
Meanwhile, Scotland Yard said it was preparing a "detailed response" to questions from London mayor Boris Johnson about why the force did not inform the peer's family he had been cleared before he died from cancer earlier this year.
Lord Brittan's brother, Sir Samuel Brittan, called on Mr Watson, now deputy leader of the Labour Party, to apologise after police dropped an inquiry into allegations that Lord Brittan raped a 19-year-old student in 1967.
But writing on the Huffington Post website, Mr Watson outlines his belief that he acted appropriately.
He writes: "As the tributes flowed in from his lifelong friends I felt for those people who claimed he abused them.
"I repeated a line used by one of the alleged survivors, who said, 'He is close to evil as any human being could get'. I shouldn't have repeated such an emotive phrase.
"The choice facing anyone who is presented with testimony of this kind is whether to pass it on to the authorities and urge them to investigate or to ignore it.
"I chose the first option. I felt it was my duty to do so."
Mr Watson added he contacted the DPP in 2014 because he felt the allegations he had been made aware of against Lord Brittan "should be fully investigated".
The MP stated he was sorry for the "distress Leon Brittan's family experienced as they grieved for him" as a result of the claims.
He also outlines his belief that Lord Brittan "would have been interviewed even if I hadn't intervened because the DPP made it clear in her reply to my letter that the police investigation into him was ongoing".
The Crown Prosecution Service (CPS) found in July 2013 that there was not enough evidence for a prosecution, but the decision was never passed on to the peer.
The case was reopened last year after Mr Watson wrote to the DPP and police later interviewed Lord Brittan under caution, when he was seriously ill.
A CPS spokesman said: "The DPP received a letter from Tom Watson MP in May 2014. The majority of the concerns raised by Mr Watson were operational matters concerning the police.
"As such, the DPP simply confirmed to Mr Watson that she would forward his correspondence on to the police to address. The CPS has no power to direct the police in operational matters, including the conduct of a criminal investigation, and the decision to interview a suspect is a decision for the police alone."
A senior Scotland Yard officer wrote to Lord Brittan's widow this weekto apologise for failing to tell the family the peer had been cleared.
Mr Johnson said: "I welcome the fact that the Met has now apologised to Lady Brittan. It's clear the delay in informing her that there was no case to answer is completely unacceptable and I have raised the matter with the Commissioner."
Scotland Yard said: "The Metropolitan Police Service is preparing a detailed response to the mayor of London's request for an explanation in the delay in informing the widow of a man in his 70s investigated for rape that there was insufficient evidence to proceed to a charge.
"The MPS expects this response will be given to him next week, once all the material has been reviewed."