Complaints were made against an activist in a Tory bullying scandal at least eight months before the party says it first knew of the problem, an ex-aide says.
A senior aide to ex-Tory chairman Grant Shapps says two activists complained about the behaviour of Mark Clarke.
He was this week banned for life from the party after accusations of bullying, harassment and blackmail.
Mr Clarke denies all such allegations.
Paul Abbott, Mr Shapp's former chief-of-staff, says he also complained about Mr Clarke's behaviour himself in 2014, and says he has been "repeatedly threatened" as a result. "He is an appalling man and I wish I had never met him," he said.
The party has been engulfed in allegations of bullying, sexual assault and intimidation since a young activist, Elliott Johnson, took his own life in September.
Mr Johnson had complained a month earlier to the party that he was being threatened by Mr Clarke, who ran Road Trip, an organisation which bussed young Tory volunteers around the country to help in the election campaign.
Mr Abbott said the complaints from activists in 2014 did not include allegations of a sexual nature or blackmail: "He was just rude, and a nightmare to deal with."
He says he passed on his concerns and urged the activists to make a formal complaint.
Mr Abbott's account is significant because it appears to be at odds with the party's insistence that it only became aware of the problems around Mr Clarke when party chairman Lord Feldman received a batch of complaints in August. Lord Feldman says he had been "wholly unaware" of the allegations around Mr Clarke.
The disclosures also raise awkward questions for Mr Shapps, currently a minister at the Department for International Development, who was co-chair of the party from 2012-15, and responsible for its campaigning functions.
BBC Newsnight has also learned that the official internal report into Mr Clarke's candidacy in the 2010 election contained evidence of what one party worker described as "extreme aggressive behaviour, verging on violence".
In a submission for the candidate report on Mr Clarke, a party staffer who worked with him during his campaign to become MP for Tooting, described an incident at an internal party conference.
The worker told party officials: "I attended an event with Mark Clarke where he singled me out, started shouting at me in a packed room. We went outside where he pushed me against a wall and screamed in my face."
Mr Clarke had formerly been on the party's "A list" - a rota of party-approved candidates. After the report was completed, Mr Clarke was not invited back onto the list.
The report was compiled whilst Lord Feldman was co-chairman of the party, alongside Baroness Warsi.
The fact that senior party officials had written evidence of bullying claims against Mr Clarke as long ago as 2010 will put pressure on the party to explain why he was given a key campaigning role - and party funding - in 2014.
Newsnight understands that Mr Clarke met with senior Conservative officials to talk about Road Trip - Clarke's idea of bussing around young activists to marginal seats, in early 2014.
Mr Clarke was asked about several allegations that were made when he was a party candidate in Tooting. He claimed to have "changed" since 2010, and also said that some of the allegations had been false.
Soon after this meeting Road Trip was officially endorsed by the party and Mr Clarke asked to head up Road Trip. A Conservative Party spokesman said that Mr Shapps "asked Mark Clarke to work in conjunction with the Party's Team 2015."
Mr Shapps is currently travelling in Sudan and could not be reached for comment.
Tory MP Ben Howlett told Newsnight on Wednesday that party bosses had failed over five years to act on complaints and warnings about Mr Clarke, and that the party's youth wing had a culture of "institutional bullying".
Newsnight has spoken to five more activists who say they made complaints about Mr Clarke before Mr Johnson's death.
Mr Clarke says he strongly refutes all allegations of bullying, harassment, assault or attempted blackmail.
He said: "I believe that these false allegations and this media firestorm are related to the events surrounding Elliott's sad death. As such I will be co-operating with the coroner and providing him with the fullest information. This is the proper process. After the inquest I will look to take legal action for defamation in respect of these allegations."