Mordaunt, a member of Parliament and communities minister, delivered her speech on "cock welfare" after losing an unspecified bet to a group of Royal Navy officers, the Daily Mail reported on Saturday.
At magazine awards dinner, the MP explained: "[D]uring our mess dinner at the end of the course, I was fined for a misdemeanour," the Mail quoted the lawmaker, who is a Navy reservist herself.
"The fine was to say a particular word, an abbreviation of cockerel, several times during a speech on the floor of the Commons, and mention all the names of the officers present," she said.
The paper also reported that several Labour party members have castigated Mordaunt for her parliamentary prank.
"She should realise that the House of Commons is not a TV reality show," former Labour Minister Kate Hoey told the Mail.
Watch the innuendo-laden speech below: