The Conservatives have been accused of withholding the contents of an internal bullying inquiry from police by the father of a young activist who took his own life.
Ray Johnson, whose son Elliott campaigned for the Tories in the 2015 general election, said the party is "determined to keep everything under wraps" surrounding events leading up to the 21-year-old's death.
A law firm commissioned by the party to investigate allegations of bullying and the handling of several complaints about a key activist in the youth campaign returned its report in August.
However Mr Johnson said the full report had not been handed over to police, despite more than one request being made.
He told the Daily Mirror: "This is a huge amount of evidence the Tories want to keep quiet. It shows they are a very secretive party and are determined to keep everything under wraps."
The Conservative Party said it had released "as much of the report as was possible", without publishing information that would lead to the identification of witnesses who gave evidence on condition of anonymity.
Mr Johnson said Tory party chairman Sir Patrick McLoughlin wrote to the family in October promising to help the police in any investigation.
"He should volunteer this evidence to the police as it may contain information that may be helpful in their investigations," Mr Johnson told the newspaper.
A British Transport Police spokeswoman told the newspaper that they could "confirm we made requests for the report but have not yet received it".
Mr Johnson was hit by a train and killed at Sandy station in Bedfordshire on September 15 2015, just weeks after making allegations about his treatment within the Tory party.
Prior to the general election he worked on a campaign taking young activists around the country in support of Conservative candidates.
The Clifford Chance investigation found party activist Mark Clarke, the so-called "Tatler Tory", was appointed to lead the RoadTrip campaign despite warnings of his past record of "aggressive" conduct.
The probe found that complaints were made about the conduct of Mr Clarke on seven occasions before the party finally mounted an investigation into his behaviour.
The report said the party's then co-chairmen Lord Feldman and Grant Shapps had not been made aware of the allegations until August 2015 when an internal party inquiry was launched.
It noted Mr Shapps had seen an internal party report which referred to Mr Clarke's past "aggressive and bullying conduct" when he appointed him to head a Conservative youth campaign drive.
Mr Clarke, who has always denied the allegations against him, refused to be interviewed by Clifford Chance, although his solicitors told the inquiry he was continuing to co-operate with the police and coroner investigating Mr Johnson's death.