MI6 failed to warn the UK’s foreign secretary that a “high risk” agent had been engaged in "serious criminality" while operating overseas, an independent watchdog said.
The spy agency failed to be fully transparent when trying to licence the operative's activities under the Intelligence Services Act, the Investigatory Powers Commissioner said.
The agent, probably an undercover informant in an undisclosed country, had previously been warned by MI6 that breaching its red lines would result in the end of their relationship.
But when the agent's conduct fell short, MI6 failed to make their criminality "expressly clear" to Whitehall when it tried to renew their authorisation.
The Commissioner, which examines the use of covert powers by Britain's intelligence services, revealed the incident in its annual report.
MI6 had been seeking to authorise the agent’s activities under Section 7 of the act, sometimes called the “licence to kill”.
The controversial section allows agents to break any law abroad without the threat of legal action at home, as long as they have written permission from the foreign secretary.
The authors agreed that the red lines set out previously had "probably been crossed”.
The report also looked into claims that MI6 had been forced to suspend co-operation with another country after a detainee there was subjected to “unacceptable treatment” during an anti-terror operation.
MI6 says further protection had been introduced allowing them to resume activities there.
Sir Brian Leveson, the Investigatory Powers Commissioner, said: “On the whole, I have been impressed by the high level of compliance with the legislation and Codes of Practice.
"I am confident that we … can continue to provide a high standard of scrutiny and oversight to ensure that the use of covert powers within the UK fully complies with its human rights obligations.”
