South Northamptonshire MP Andrea Leadsom was allegedly called "a stupid woman" by the speaker of the House of Commons.
John Bercow, who faced allegations of bullying earlier this month, reportedly made the comment under his breath during a heated discussion after Prime Minister's Questions about the timetabling of Government business.
Labour complained to the speaker that a statement on the East Coast Main Line rail franchise was deliberately scheduled to limit time for its own "opposition day" debates on the Grenfell Tower fire and the release of Brexit documents.
Buckingham MP Mr Bercow criticised the frontbench and said nothing would stop him from upholding the rights of backbenchers to hold the Government to account.
It is at this point the speaker is alleged to have called the South Northamptonshire MP a “stupid woman”, who in her role as Leader of the House of Commons, is responsible for the debating schedule.
Mrs Leadsom said: "I'm determined to change the culture of Parliament and in setting up an independent complaints procedure I hope that we will, in future, have a workplace in Parliament that treats everybody with the dignity and respect they deserve."
A spokeswoman for Mr Bercow's said: "Wednesday was an unusual and controversial day in how business was handled in the house by the Government and some strong and differing views were expressed on all sides on the subject.
"The speaker treats his colleagues with respect and strives at every turn to facilitate the House of Commons."