Interrupting Theresa May’s keynote speech to Tory members in Manchester, Lee Nelson – real name Simon Brodkin – approached the podium to hand the Prime Minister the fake document before being led away.
Conservative MPs voiced their concerns over the prank, as party chairman Sir Patrick McLoughlin and Home Secretary Amber Rudd promised a full inquiry.
“There should be some very serious questions – that could have been a terrorist,” said Tory MP George Freeman, the head of the Prime Minister’s policy board.
A Conservative spokesman said: “In light of the arrest during the Prime Minister’s speech we are working with the police to review the accreditation process and security arrangements for party conference.”
Mr Brodkin, who has a history of interrupting high-profile events, was arrested “to prevent a breach of the peace” after being escorted out of the conference hall, but was later released.
He was revealed to have had legitimate accreditation for the Conservative conference, believed to be a two-day delegate pass costing around £700.
Greater Manchester Police chief superintendent John O’Hare said: “The man had legitimate accreditation which granted him access to the conference site.
“In light of this we will be reviewing the accreditation process with the Conservative Party.
“Even with accreditation, everyone at the conference goes through airport-style searches before being allowed entry to the site.”
Security firm G4S defended themselves, using their Twitter account to reveal they were not the security provider for inside the auditorium but only the conference perimeter, entrances and exits.
Mr Brodkin was given a conditional caution in March 2013 after warming up alongside Premier League footballers ahead of a Manchester City game at Everton.
He was also arrested, but later released, when he threw money at world football boss Sepp Blatter in July 2015.
A month earlier, Mr Brodkin stormed the stage during Kanye West’s set at Glastonbury festival.