DUP MP Carla Lockhart was pulled up on her use of language in the House of Commons by referring to the Prime Minister as "you".
During Prime Minister's Questions she referred to an interview Mr Johnson had with Sky News in December 2019.
"You pledged, there would be no checks on goods entering from NI to GB or GB to NI," she said.
"While this has proven more challenging to deliver in practice, would you wish to take this opportunity to encourage ministers in Northern Ireland to do all they can..."
She was cut off by Speaker Lindsay Hoyle calling "order".
"Unfortunately," he said.
"I am not responsible and 'you' is not something we should be using."
Ms Lockhart, the representative for Upper Bann since December 2019, offered her humble apologies for the indiscretion before continuing on.
Prime Minister Boris Johnson pledged his government would do all they could to ensure free-flowing trade across the Irish Sea in response to her question.
A Commons factsheet on traditions in the House of Commons says the term "you" when addressing someone should only be used for referring to the Speaker and "honourable member" is preferred when addressing another MP in order to "maintain the dignity of the House and its members, to make criticism and comment less direct as well as showing respect to the chair".
The so-called bible of parliamentary procedure, Erskine May advises on all aspects procedure and constitutional conventions for MPs in the Commons.
On how members should address each other, it states no one other than the chair should address another member by their name in order to guard "against the appearance of personality of debate".
It adds: "Each Member must be distinguished by the office they hold, by the place they represent or by other designations, as ‘the Leader of the Opposition’, ‘the noble Lord the Secretary of State for Foreign and Commonwealth Affairs’, ‘the (right) honourable gentleman the Member for York’, or ‘the honourable and learned Member who has just sat down’ or, when speaking of a member of the same party, ‘my (right) honourable friend the Member for...
"Former practices of referring to QCs as ‘learned’ and to Members who have served in the armed forces as ‘gallant’ are no longer widely used."