Caroline Lucas notched up a significant victory in her campaign against the London arms fair taking place this week, after two companies were kicked out of the DSEI event.
MagForce International, a French company, and Chinese firm Tianjin MyWay International Trading were forced to leave the Docklands event for promoting illegal weapons.
Lucas, the Green party's only MP, had complained about the issue in the Commons after prime minister's questions, saying the companies were selling "illegal weapons of torture".
Its products being promoted at DSEI included handheld projectile electric shock weapons, weighted leg cuffs and stun batons.
"It's incredibly worrying that it takes a question in parliament for action to be taken when there was clear evidence of items being promoted illegally," Lucas said.
"Time and again the organisers of DSEI have shown that they cannot guarantee that exhibitors will remain with the law.
"The government is supposed to regulate this event and has shown startling complacency."
DSEI said the companies' stands had been taken down and their staff removed from the fair.
"This action highlights our commitment to ensuring that all equipment, services, promotional material, documentation and anything else on display... complies with domestic and international law," a spokesperson said.
Responsibility for enforcing the law at DSEI rests with HM Revenue and Customs, which has confiscated the literature and investigating the matter further.
But Lucas' concerns have highlighted the anger many feel about Britain's high-level involvement in the arms trade.
"The DSEi arms fair facilitates arms sales from anywhere to anywhere," the Campaign Against the Arms Trade's parliamentary coordinator Ann Feltham wrote in a comment piece for Politics.co.uk.
"If the deals made do not involve equipment exported from the UK, the UK government has no control over them - madness compounded."
MPs will debate UKTI's involvement in organising the arms fair this afternoon.