Theresa May regards Speaker John Brecow's alleged attack on a senior minister as a "stupid woman" as "unacceptable", Downing Street has said.
Mr Bercow is said to have called the Leader of the House Andrea Leadsom "f****** useless" in an aside in the Commons chamber on Wednesday.
A No 10 spokeswoman said: "We have seen the alleged remarks.
"Clearly the Prime Minister thinks they are unacceptable. If an official complaint is made it should be properly investigated."
A Westminster source said there were "no plans" for Mrs Leadsom to complain "at the moment".
Mrs Leadsom said: "I am focused on ensuring that anyone who is bullied or treated unfairly in Parliament is able to come forward and have their concerns and complaints dealt with in a rigorous and fair manner."