Celebrity doctor Christian Jessen has removed a controversial tweet about First Minister Arlene Foster from his social media account.
However, last night media lawyer Paul Tweed, who is acting for Mrs Foster, said: "I can confirm that Dr Jessen has been put on notice that we are in the process of issuing defamation proceedings in the High Court in Belfast.
"He had been afforded every opportunity to take down his post and apologise but he didn't do so until belatedly."
The television presenter had been threatened with legal action after tweeting an unfounded rumour about the DUP leader last month.
Several individuals, who Mrs Foster intends on suing for libel, have been identified by her legal team.
Dr Jessen was among this group after receiving a warning of impending High Court action.
The tweet, which was posted on Monday, December 23, was still viewable until recent days and had been retweeted around 500 times.
Dr Jessen removed the post from his Twitter account within the past week.
The day after Dr Jessen posted the tweet Mr Tweed replied: "I am putting Dr Christian Jessen on notice in relation to a totally false allegation he has tweeted regarding DUP leader and former NI First Minister, Arlene Foster.
"Legal action will also be taken against any persons who have retweeted this highly defamatory allegation."
In a follow-up statement, he added: "I would confirm, if necessary, legal proceedings will be taken against Dr Christian Jessen, Twitter and any persons who have recklessly retweeted this false and highly defamatory allegation."
Dr Jessen, who is best known for presenting Channel 4 programmes Embarrassing Bodies and Supersize v Superskinny, now appears to have acted upon the warning by Mr Tweed.
Mrs Foster has previously been the target of abuse on social media. In July Gerard Traynor, from Oldham in Greater Manchester, was jailed for targeting her online and urging her to kill herself, having also racially abused the Home Secretary Priti Patel.
In the wake of the case the Fermanagh and South Tyrone MLA called for social media platforms like Facebook and Twitter to do more to tackle online trolls and said the abuse she received had left her children very upset.
Responding to Traynor's 22-month jail term imposed at Manchester Crown Court, Mrs Foster told the Belfast Telegraph that she had stopped looking at her social media accounts because of the level of trolling directed at her.
"The internet is a very dark place," she said. "Obviously it has brought a lot of good in that everyone is connected nowadays, but it also brings out the worst in some people."