Roger Bird received an early Christmas present on 23 December when he was cleared by an external investigation into allegations that the Ukip general secretary had sexually harassed Natasha Bolter, a Labour-defector turned poster girl and parliamentary candidate for Nigel Farage’s party.

Mr Bird, 41, had been suspended from his post at Ukip’s Mayfair headquarters two weeks earlier when Ms Bolter went public with her claims, including one alleging that Mr Bird had propositioned her at his London club during her selection interview when the pair met for the first time.

It soon emerged that a six-week relationship that began some time later was entirely consensual and Ms Bolter, 39, was found to have invented various stories about her life, such as a claim to have studied at Wadham College, Oxford.

Mr Bird was quickly cleared and wanted his £75,000 a year job back. Ukip thought otherwise and tried to sack him.

The Independent can reveal the inside story of how Mr Bird was pushed out – amid claims from his allies that he was doomed before the scandal erupted, having made enemies two of the most powerful figures in Ukip – party secretary Matthew Richardson and treasurer Andrew Reid,

These men are said to have taken exception to the successful internal reforms he established after his promotion to one of the party’s most senior positions last July.

Ukip officials also failed to tell Mr Bird the company that carried out the investigation into the sexual harassment claims, HRx Consultancy Services, is closely connected to a leading Tory activist.

The firm is run by Victoria Walker, the sister of former Tory councillor Donal Blaney, who is not only chief executive of both The Margaret Thatcher Centre and campaign group Conservative Way Forward, but also co-founder of Young Britons’ Foundation (YBF), which has close links to US neoconservatives.

Mr Blaney, 40, who has described YBF as “a Conservative madrasa” that radicalises young Tories, is also the head of Kent-based Griffin Law where Mrs Walker, 36, works as a HR consultant in addition to her work at HRx. Mrs Walker led the investigation into Mr Bird.

Her preliminary investigation was carried out prior to Mr Bird’s suspension and it found no evidence to support Ms Bolter’s sexual harassment claims. Mr Bird was also cleared of any impropriety in the candidate assessment process. Despite this, communications seen by The Independent show that Mr Bird was told that he had brought Ukip into disrepute, as evidenced by a drop in Nigel Farage’s opinion poll ratings in December. The party, assisted by HRx, then suspended Mr Bird and widened the investigation to include the disrepute charge.

Initial press reports about their relationship suggested that Mr Bird abused his position by incorrectly approving Ms Bolter’s candidacy – but we can reveal that he was the only official who failed her during the four-stage process.

“A panel of three people – Peter Reeve, the Local Government spokesperson, Chris Adams, the South-east regional organiser, and press officer Jack Duffin were the ones who approved Natasha’s candidacy at the first two stages on 10 September,” the party source said. “It was Roger who failed her for the third stage and recommended getting her back in that day for reassessment.”

Ms Bolter narrowly passed the retests, and was approved. The two subsequently embarked on consensual relationship, which fizzled out.

Friends of Mr Bird were then amazed when a supposed scandal involving two divorcees, both single, dominated the media for days in early December.

“Roger was never in doubt that he could show exactly what happened,” said the party source. “He was cleared of the sexual harassment allegations – but it didn’t matter by that stage. The powers that be wanted him out, as shown by the investigation continuing and broadening.”

Mr Bird eventually left Ukip by “mutual consent” with both parties signing confidentiality agreements. A friend of Mr Bird’s said: “Roger was an appointee of Nigel himself but was given a duff hand. Roger did not actually have any power, including hiring and firing, but was expected to solve the numerous problems in Ukip.

“Roger’s reward for being trustworthy, even-handed and cool-headed was to earn the ire of two key factions: one lead by the party chairman Steve Crowther and the ‘old guard’ who wanted him to take Ukip back to some Tory party in exile and who considered saving a deposit in an election as a victory.”

Mr Bird said last night: “The process of my departure was very much both mutual and amicable. I remain a very enthusiastic member of the party and look forward to campaigning for our candidates in May. It’s unfortunate I wasn’t able to continue in the role but I’m sure I’ll find other ways of helping the party.”