Commons Speaker John Bercow has been accused of calling a senior minister a "stupid woman" after warning the Tories against "abuse" of Parliamentary debate protocol.
During discussions following Prime Minister's Questions on Wednesday, some MPs claim Mr Bercow called Leader of the House Andrea Leadsom a "stupid woman" and "f****** useless" in a muttered aside.
The alleged comment came after he openly berated her for the way ministers were conducting government business.
Labour had scheduled a debate on the Grenfell Tower fire - but their chief whip, Nick Brown, complained about a government statement being read out during the same slot.
He said ministers were repeatedly violating the convention that time reserved for opposition debates should not be taken up with statements on government business.
Staring at Leadsom, who could be seen sitting on the front bench looking away, Mr Bercow agreed that it was an "an undesirable state of affairs", and warned he would take action in future.
- Watch: Speaker warns ministers against 'abuse' of debate system
"If it were to happen on further occasions, a great many honorable and right honorable members, not to mention interested parties in the opposition day debates outside the chamber, would view it, frankly, as an abuse," he said.
"I hope that that message is heard loudly and clearly on the government frontbench, at the highest level, by the people in particular by whom it needs to be heard.”
He went on that he would use the power of the position of Speaker to "facilitate the rights of the House in other ways" were it to happen again.
One unnamed MP, who said they had heard Mr Bercow's muttered comments, told The Daily Telegraph: "He said 'stupid woman' and went on to say either 'f****** useless or f****** outrageous', but I am clear that the words 'stupid woman' were said, and I am clear that the word 'useless' was said.
"I thought what I was witnessing was entirely outrageous."
The Speaker's office acknowledged "strong and differing views" had been expressed in the chamber on what it said had been an "unusual and controversial day" in Parliament.
However, it added, the Speaker "treats his colleagues with respect" and "strives at every turn to facilitate the House of Commons."
The incident came on the day an inquiry into allegations Mr Bercow bullied two former private secretaries, Angus Sinclair and Kate Emms, was blocked by MPs.
The Commons Standards Committee voted three-two against allowing Parliament's watchdog to investigate the allegations, which he has consistently denied.