Democratic Unionist Party (DUP) leader Arlene Foster is suing TV presenter Dr Christian Jessen for defamation, saying he made an “attack” on her marriage.
On 23 December 2019, Dr Jessen tweeted an allegation that Mrs Foster had been having an extra-marital affair.
The post remained online until Dr Jessen deleted it on 7 January 2020.
On Wednesday Mrs Foster told the High Court in Belfast it had been a “very humiliating” time for her. Judgement has been reserved in the case.
Mrs Foster is a member of the Northern Ireland Assembly for Fermanagh and South Tyrone and the first minister of Northern Ireland.
Dr Jessen is best known for presenting Channel Four programme Embarrassing Bodies.
There was no representation on behalf of Dr Jessen in court on Wednesday and the court was told 13 separate approaches by letter and email to Dr Jessen had gone “unanswered”.
Giving evidence to the court, Mrs Foster said she had initially been made aware of the tweet by her director of communications, who handles her social media accounts.
The first minister described it as “an attack on me personally and my marriage, meant to destabilise me at a very critical time”.
At that time Mrs Foster was heavily involved in talks to restore power-sharing in Northern Ireland.
The court was told Dr Jessen’s tweet was published at about the same time that anonymous Twitter users were claiming that Mrs Foster had been having an affair with one of her security guards.
She said having to explain to her husband what had happened was “very upsetting”.
“It was very humiliating to see that the relationship that’s most important to me had been trashed if you like and put out there in the public domain in that fashion,” she told the court.
“One of the things that gives me stability is my home relationship – it was almost as if this cut to the very core of my life.”
The court heard Dr Jessen had more than 300,000 followers on Twitter in December 2019 and that the tweet had been retweeted more than 500 times.
Mrs Foster said “there wasn’t much sleep on the night of the 23rd” of December when the tweet was posted and that she had to have conversations with her children, husband and mother about what was happening.
She said her family had attended church together on Christmas Day and that she later found out that a journalist had contacted her church minister to ask how her family “had appeared” that day.
The court was also told Dr Jessen’s tweet had referred to Mrs Foster as “the sanctity of marriage preaching woman”, adding: “It always comes back to bite them on the arse in the end.”
It was in relation to the DUP’s opposition to same-sex marriage.
Asked if she believed in the sanctity of marriage, Mrs Foster said she did but rejected accusations that she was homophobic.
The judge said there was a “big difference between holding strong religious views on the sanctity of marriage and having an irrational hatred of homosexuals”, and said the DUP leader would have been aware of that.
Mrs Foster replied: “I do get distressed when people call me a homophobe because that’s something I am not.
“I have many friends who are homosexual, they know my views and in any event same-sex marriage is now the law in Northern Ireland and has to be upheld.
“I have never in my own utterances said anything in relation with people who are homosexual and that’s why I do get upset when people call me a homophobe.”
She told the court she did not know Dr Jessen and that even when he had removed the tweet there was “no acknowledgment of wrong-doing”.
Mrs Foster’s barrister David Ringland QC said a solicitor for the DUP leader had contacted Dr Jessen on Twitter instructing him to remove the post on 24 December but he had refused to do so.
Mr Ringland said the tweet was not removed until 7 January, when Dr Jessen responded to follow-up requests in a “pithy email”.
The court was told Dr Jessen had said he did not agree with the suggestion his claim gave rise to defamation and that he had removed it without admission of liability.
Mr Ringland said there was “no correction, retraction or apology” and that Dr Jessen had taken a “head-in-the-sand approach”.
The judge reserved judgement but said he would seek to deal with the case as a “matter of urgency”.