The Conservative Party has denied knowledge of Ross England's involvement in a rape trial collapse before he was selected as a candidate.
Mr England was accused by a Crown Court judge of deliberately sabotaging the trial in April 2018, by making claims about the victim's sexual history.
The defendant, James Hackett, was convicted following a retrial.
Sources had told BBC Wales the party knew about his involvement, but the Welsh party chairman denied this.
In the first of two statements issued on Thursday evening, Lord Davies of Gower said the party only became aware of the "full extent of the proceedings" when Hackett's appeal process ended earlier this month.
He said: "We were fully aware that Ross England was involved as a witness in a sensitive case. We are also aware of the responsibility we have as employers.
"Since the end of the Appeal Court case, we have now been made aware of the full extent of the proceedings."
In a second statement, he said he could "categorically state" that he and Welsh Secretary Alun Cairns were "completely unaware of the details of the collapse of this trial until they became public this week".
Mr England used to work for Mr Cairns in the Vale of Glamorgan, and was selected as the party's candidate to fight for the constituency seat at the 2021 Welsh assembly elections.
Mr Cairns also told BBC Wales he only became aware of Mr England's role in the trial's collapse when the story broke earlier this week.
The party has suspended Mr England as a candidate and an employee and a full investigation will be conducted.
He has said he acted honestly during the aborted trial, and was not aware that any evidence had been ruled inadmissible.
Speaking to BBC Wales on Thursday, one Conservative Party source said they called the party's Cardiff headquarters on the day the trial collapsed to inform management that Mr England's actions had led to that happening.
He had been giving evidence at the trial of his friend, when he claimed to have had a casual sexual relationship with the victim, which she denies.
The judge Stephen Hopkins QC stopped the trial, asking Mr England: "Why did you say that, are you completely stupid?"
The judge continued: "You have managed single-handed, and I have no doubt it was deliberate on your part, to sabotage this trial… get out of my court."
The judge added he would be writing to Mr England's political allies in the hope they would take "appropriate action".
A separate source told BBC Wales: "Richard Minshull [Director, Welsh Conservatives] got a letter around this timeframe about Ross because the party were his employer.
"Whether this letter was from the judge or not, I'm not sure, but he was certainly speaking with both Alun [Cairns - Welsh Secretary] and Byron [Lord Davies, chairman of the Welsh Conservatives] regularly regarding 'what to do about Ross.'"
The victim has told BBC Wales that "people in Conservative HQ know... I know that Alun Cairns knows what he did in court and they knew by that evening.
"Therefore for them to make him a candidate in their target seat for the Welsh assembly proves to me how little respect they have for me, how little respect they have for the criminal justice system."
Analysis: Felicity Evans, BBC Wales political editor
After three days of virtual silence, two statements from the Welsh Conservatives in two hours.
The last emphatic in its denial that neither Lord Davies, the party chair, nor Alun Cairns, the Welsh Secretary had any knowledge of the details of the collapsed rape trial until they were reported in the media this week.
The party will hope this draws a line under a hugely damaging row, just as they're about to embark on a general election campaign.
In April 2018, Ross England was working for the party when a Crown Court judge accused him of deliberately sabotaging a rape trial, precipitating a retrial.
The party say they were "fully aware" he was a witness in a sensitive trial and of their responsibility as an employer.
If, despite that full awareness, his employers did not realise for 18 months he'd caused the collapse of a criminal trial and been thrown out of court by the judge, it raises fundamental questions about supervision, vetting and candidate selection processes.
Mr Cairns has previously endorsed Mr England as a "friend and colleague" with whom "it will be a pleasure to campaign".
On Thursday, he said he only became aware of the collapse of the trial "some considerable time afterwards and had no knowledge of the role of Ross England".
Lord Davies said "continued speculation from an unspecified source" about what party officials or elected representatives knew was "unhelpful".
He also said "at no time" had any party officials received any correspondence in relation to the matter.
"As soon as it came to my attention, we acted immediately," he added.
"As chairman of the Welsh Conservative Party, I take all allegations concerning members, officials and elected representatives extremely seriously."