Agent provocateur

a secret agent hired to incite suspected persons to some illegal action, outbreak, etc., that will make them liable to punishment.
Contemporary Examples

Once she overcame her shock, Esfandiari realized she was arrested because she was perceived as an agent provocateur.
My Iranian Prison Sandra McElwaine September 24, 2009

“We basically associate ourselves as the La Perla or the agent provocateur for the transgender community,” Lauz said.
Introducing the First Lingerie Line for Transgender Women Claire Stern February 4, 2013

Her sensibilities tend more toward, say, an agent provocateur bustier than business wear.
Inside the High-End Fashion Sensibility on CBS’s ‘The Good Wife’ Jace Lacob October 22, 2012

Historical Examples

He found discrepancies in the accounts, and intimated that the Government had adopted the odious rôle of the agent provocateur.
The Annual Register 1914 Anonymous

Galban seized the opportunity to bring his talents as agent provocateur into the field.
The Green Book Mr Jkai

I was looking about to find the German agent provocateur, but I failed to find him.
Spies of the Kaiser William Le Queux

Was Reese merely a “stool pigeon” or was he an “agent provocateur?”
The Everett massacre Walker C. Smith

The proper business of an ‘agent provocateur’ is to provoke.
The Secret Agent Joseph Conrad

The seditious placards posted up at Norwich may have been the work of some fanatic or of an agent provocateur.
William Pitt and the Great War John Holland Rose

They seem to find some pleasure in admiring him in the part of agent provocateur.
Bismarck and the Foundation of the German Empire James Wycliffe Headlam

noun (pl) agents provocateurs (aʒɑ̃ prɔvɔkatœr)
a secret agent employed to provoke suspected persons to commit illegal acts and so be discredited or liable to punishment