British PM Theresa May's speech at the Conservative Party conference descended into chaos after a TV prankster interrupted her appearance to hand her a fake P45, British media report.

The Prime Minister was forced to pause her keynote address to the Tory gathering after Simon Brodkin handed her the sheet of paper.

Brodkin appeared to be posing as a photographer in the media scrum gathered below May's lectern. He picked up his camera briefly before putting it down and handing her the paper, which May took from him.

He was quickly escorted from the hall by security to shouts of "out, out, out" from the audience and was later arrested by police, Tory officials confirmed.

Caught off guard by the prank, May re-read a line from her speech before responding that she planned to give a P45 - the form handed out by an employer when a staff member leaves their job - to the Labour leader, Jeremy Corbyn.

Brodkin tweeted that the P45 was handed to Ms May on behalf of Boris Johnson, whose public commentary on the Prime Minister's Brexit strategy led to suggestions he had her job in his sights. 

A close-up photo of the fake P45 showed it listed the “reason for termination” as “neither strong nor stable”.

Johnson's own future in the Cabinet has been called into question following perceived attempts to undermine the Prime Minister and her approach to Brexit.