Tory chairman Lord Feldman is facing fresh calls to resign amid claims he was handed a dossier detailing a culture of bullying within the Conservative Party's youth wing in 2010.
Two people involved in producing the document claimed it named Mark Clarke, an activist expelled from the party last month following allegations of bullying, which he strongly denies.
Lord Feldman insisted that he had not been made aware of allegations about Mr Clarke's behaviour until August 2015.
Activist Elliott Johnson, 21, a member of the Conservative Future youth wing, was found dead on railway tracks in September.
A month earlier he had alleged bullying and his death sparked an investigation and the resignation of former party chairman Grant Shapps.
Ray Johnson, Elliott's father, has renewed his demands for the peer to quit, saying if the dossier is true he "must have known earlier" about bullying in the party.
"If the detail is true and Mr Feldman is aware of various allegations, he really should look to his responsibility for the Conservative Party and for my family and take the decision to resign his position," he told BBC Radio 4's Today programme.
Mr Johnson said he had received a "bland" letter from Lord Feldman about his son's death.
He criticised the Conservative Party for the way it had treated his family, saying they had been "left adrift".
"It's almost as if they had closed the door, shut the windows and hunkered down to weather the storm. I think that they were hoping that this would go away and if it wasn't going to go away they were intent on a cover-up."
BBC Two's Newsnight reported that the 2010 dossier was given to Lord Feldman by Ben Howlett, who is now a Tory MP.
Patrick Sullivan, who now runs a right-of-centre think tank, said hard copies of the 2010 dossier were handed to Lord Feldman and then Tory co-chair Baroness Warsi.
Mr Sullivan told Newsnight that Mr Howlett decided to tackle widespread bullying among the party's young activists after being elected to a second term as chairman of Conservative Future, the party's youth wing, in 2010.
Mr Sullivan said: "He had a strong anti-bullying stance in the campaign because there had been a culture of bullying. As soon as he was elected, Ben and myself helped compile a dossier and that dossier was given by Ben to Lord Feldman and Sayeeda Warsi."
He added that there had been complaints about Mr Clarke even before 2010, when he was removed from the party's list of approved candidates after a failed campaign in Tooting.
"The dossier is not the only thing," Mr Sullivan told Newsnight. "There were complaints about Mark Clarke in 2008. So complaints about Mark Clarke had been something that Conservative Central Office have known about for a very long time."
Lord Feldman said: "I was wholly unaware of allegations of bullying and inappropriate sexual conduct by Mr Clarke prior to August 2015. Such behaviour is abhorrent to me and had this been brought to my attention I would have taken immediate action to investigate, as I have done since I received the complaint in August 2015."