A decision on whether to issue contempt of court proceedings over false evidence given to the High Court by an MI5 officer has been adjourned to allow time for a further investigation, Lady Chief Justice Baroness Carr has said.
Last month the intelligence agency apologised for the false evidence given in a witness statement, following a BBC investigation about a covert agent that was alleged to have abused two female partners.
The government had sought to block the BBC's investigation, but failed, resulting in anonymity for the agent instead.
During the previous legal proceeding, MI5 told three courts that it had stuck to its policy of neither confirming nor denying (NCND) that the person was an agent.
The BBC produced notes and phone call recordings showing that the intelligence agency had disclosed the man's status to them while it was attempting to prevent the publication of the investigation.
Baroness Carr said: "The investigations carried out by MI5 to date suffer from serious procedural deficiencies. Their conclusions cannot presently be relied on.
"In those circumstances, it would be premature to reach any conclusions on whether to initiate contempt proceedings against any individual.
"Consideration of that question is adjourned pending the outcome of a further investigation.
"The court considers that this further investigation should be carried out under the auspices of the Investigatory Powers Commissioner."
MI5’s explanations to the High Court about how false evidence came to be given in a witness statement were given "in a piecemeal and unsatisfactory way," Lady Chief Justice Baroness Carr said.
A senior officer had said the agency had maintained its policy of neither confirming nor denying in its dealings with BBC journalist Daniel De Simone, when it had not.
Baroness Carr said: "NCND was maintained until shortly before the hearing before us on June 3 2025, long after MI5 had filed evidence making clear that Witness A’s evidence was incorrect and any justification for its maintenance had disappeared.
"Thought should have been given at a much earlier stage to the question whether it was realistic to maintain NCND in the circumstances, particularly given that the effect of doing so was to cast formal doubt on the veracity of Mr De Simone’s evidence."
Two reviews – both internal and external – have been undertaken since the BBC revealed that MI5 had given false evidence in court.
Both inquiries absolved the agency and its officers of deliberate wrongdoing.
Following the ruling, MI5 director-general Sir Ken McCallum said: "Today, the High Court has handed down its judgment after MI5 provided incorrect witness evidence in legal proceedings.
"I wish to repeat my full and unreserved apology for the errors made in these proceedings.
"We take our duty to provide truthful, accurate and complete information with the utmost seriousness.
"Resolving this matter to the court’s satisfaction is of the highest priority for MI5 and we are committed to co-operating fully with the Investigatory Powers Commissioner’s Office and the court.
"MI5 is now embarked on a programme of work to learn all lessons and implement changes to ensure this does not happen again. This programme will build in external challenge and expertise – with independent assurance to the Home Secretary on our progress.
"MI5’s job is to keep the country safe. Maintaining the trust of the courts is essential to that mission."
