Labour frontbencher Wes Streeting has apologised to Jeremy Corbyn after suggesting the ex-party leader had "gone senile" in the Commons.
As Mr Corbyn attempted to raise a point of order after Prime Minister's Questions the shadow Health Secretary could be heard making the remark.
After it was later branded "gross" on social media, Mr Streeting said the comment was made "in jest", but admitted: "I accept in poor taste."
"I've dropped Jeremy a note directly to apologise for any offence caused," he said.
But Mr Corbyn later told JOE he was "subjected to an appalling and defamatory mental health slur" in the House of Commons.
He added: "I have now received an apology, and I have noted it. As I said in my reply, there’s nothing 'in-jest' about calling somebody senile.
"It’s not funny. It’s very serious for people suffering from dementia. He should know this as Shadow Health Secretary.
"The right thing for somebody in his position to do would be to issue a public apology to all those who may have been hurt by his comments."
It came after Rishi Sunak again used Prime Minister's Question to criticise Keir Starmer for supporting Mr Corbyn during his time as Shadow Brexit Secretary.
Later the former party leader, who now sits as an independent MP, told Mr Sunak he was grateful for his "continued rent-free tenancy" in his head.
"If he could just let me know when he intends to speak about me that'd be helpful. That's the norm in the House," he added.
Mr Sunak replied: "If he could ask the Leader of the Opposition maybe to give me advanced sight of his questions, I'll be happy to then let him know if I need to bring him up on questions of security."
Mr Corbyn made a similar comment last week and criticised the Prime Minister for giving a "wholly inaccurate representation" of his 2019 agenda on national security.
He asked Mr Sunak to correct the record and to "accurately reflect" his views rather than deliver "inventions made up by him or his office".
