Mr Beattie apologised on Sunday for the tweeting the joke on Saturday evening.
Don't Miss
Most Read
Trending on GB News
A Stormont minister said his wife was left disgusted after one of his political rivals tweeted a joke about her that referenced a brothel.
DUP minister Edwin Poots said the tweet by Ulster Unionist leader Doug Beattie was “incredibly hurtful”.
Mr Beattie apologised on Sunday for the tweeting the joke on Saturday evening.
The Upper Bann MLA, who has deleted the tweet, reiterated that apology on the floor on the Assembly on Monday, insisting he was “truly sorry”.
The joke described a fictional scenario involving Mr Beattie and Mr Poots in a barbershop.
It made a reference to Mr Poots’ wife and a brothel.
Mr Beattie claimed the joke was not his own and he was sharing something that had been sent to him.
Mr Poots said he accepted Mr Beattie’s apology but he questioned his “poor” judgment in posting it in the first place.
“I just don’t know what he was thinking about,” he told BBC Radio Ulster.
“I’m a big boy, I can take a lot of abuse in politics and that’s fine, but we really shouldn’t be drawing other members of people’s families into anything, they have their right to their private life and, unfortunately, that has been infringed when it comes to my family in this instance.”
Mr Poots said his wife Glynis, a nurse, was “disgusted” by the tweet.
“But it’s actually had a bigger impact on the rest of us, her children and myself,” he said.
“Saturday night was the first time our family had been together as a family for four years because we have two children who are doing voluntary work abroad, and it coincided that they happened to be home.
“We got news of that late on Saturday night and to have someone described a prostitute, or your mother described as prostitute, it’s not something that people really find acceptable.
“It’s hurtful, my wife was a working class girl, not a working girl.”
He added: “Having her demeaned like that is something that personally I find incredibly hurtful.”
Mr Beattie gave a statement at the start of Assembly business on Monday.
“We must all be mindful of our language and I’ve said so on the floor of this chamber on many occasions we must guard against language that is both hurtful and harmful,” he said.
“Over the weekend I let my guard down and for that I am truly sorry.
“I posted a joke and regardless of what my intentions were, it was just inappropriate.
“It was absolutely wrong and fundamentally wrong and therefore it’s important that I stand here and I say to Mr and Mrs Poots that I am sorry for the hurt that I may have caused.
“But I have to say to wider society that my language was wrong at every level and I have to apologise to all of them.”