agent provocateur

plural agents provocateurs

1. A person who secretly disrupts a group's activities from within the group, particularly by encouraging or committing illegal acts to discredit the group or expose them to prosecution; an instigator, troublemaker.

   "This agent-provocateur business is quite foreign to British justice."

   1925 July – 1926 May, A[rthur] Conan Doyle, “In which the Reader is Shown the Habits of a Notorious Criminal”, in The Land of Mist (eBook no. 0601351h.html), Australia: Project Gutenberg Australia, published April 2019

   3 more examples

   I was told afterwards—quite possibly it was true—that agents provocateurs were touching off masses of explosive in order to increase the general noise and panic.

   1938 April, George Orwell [pseudonym; Eric Arthur Blair], chapter IX, in Homage to Catalonia, London: Secker & Warburg, →OCLC

   Suspecting that the man was an agent provocateur sent by the Prince, Pottinger told him that regrettably he had neither the knowledge nor the authority to instruct him in this or any other religion.

   1990, Peter Hopkirk, The Great Game, Folio Society, published 2010, page 50

   The criminalisation of protest has been aided by the director of public prosecution's recent guidelines on prosecuting protesters, which fail to account for the role of the police in prompting violence at demonstrations through tactics such as kettling, the use of batons, agents provocateurs and undercover policing.

   2012 March 25, Nadine El-Enany, The Guardian