Health officials feared DUP leader Sir Jeffrey Donaldson's inaccurate claims that the Northern Ireland Protocol delayed heart surgery would be "repeated for electioneering purposes".
Internal emails seen by Belfast Live show Sir Jeffrey received a letter from a health trust boss dismissing the allegations almost three weeks before he publicly withdrew his remarks.
The trail of correspondence also suggests Sir Jeffrey did not raise his allegations with either the Belfast or Southern Trust before making the claims on a live morning radio programme.
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Sir Jeffrey had claimed on BBC's Good Morning Ulster that cardiac patients in a Belfast hospital had to wait three weeks for surgery because the protocol meant equipment had to be sourced from outside the UK.
He later said the equipment problem arose in the Southern Trust and led to patients being added to a waiting list in the Belfast Trust.
But both trusts and the equipment supplier all denied the disruption was a result of the post-Brexit Irish Sea trading arrangements.
Emails show Belfast Trust drafted a statement on October 28 just hours after Sir Jeffrey's on-air claims.
Sharing the draft with colleagues, an official said: "DOH (Department of Health) officials have asked us to prepare in this way in case these claims are repeated for electioneering purposes."
Sir Jeffrey on October 31 wrote to the Southern Trust chief executive Maria O'Kane about his claims, which he said came from two doctors.
The DUP leader said he had "no desire to draw the trust into political matters" but there was a "clear public interest to be served in understanding what happened in this instance".
Dr O'Kane responded on November 2 saying that the service disruption "was in no way connected to the NI Protocol".
She told Sir Jeffrey: "I am very disappointed that you appear to have been misinformed by medical colleagues on this occasion.
"I will emphasise to all our staff the need for accuracy in all our communications so that this does not occur again."
Dr O'Kane said they "regret the disruption" earlier in the year and the "added anxiety this will have caused our patients", but stressed there have been "no further issues with the equipment".
On November 21, Sir Jeffrey expressed regret that he had placed information in the public domain that was inaccurate.
He told reporters: "I accept the trust's explanation that on this occasion it was the size of the equipment was the issue and they were able to source it from the supplier in Germany, and that the protocol on this occasion was not the problem."
The Lagan Valley MP also said he had spoken to the Southern Trust and claimed it had "apologised that the information I was given was inaccurate".
Emails show the trust was later repeatedly asked by media outlets whether it had apologised, but communications staff said that aside from an earlier statement they had "nothing further to add".
The emails were obtained through a Freedom of Information request. Neither health trust disclosed receiving any relevant correspondence from Sir Jeffrey before he made his claims on radio on October 28.
The DUP has been approached for comment.
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