The head of the United Kingdom’s domestic intelligence service, MI5, faces potential contempt of court proceedings after the agency admitted to providing false evidence in multiple court cases involving a violent neo-Nazi informant.

Sir Ken McCallum, MI5’s director-general, could be held accountable following revelations that agents lied to judges about an informant known only as Agent X. This individual, reportedly embedded by MI5 to infiltrate far-right extremist groups, used his position to threaten and physically abuse his girlfriend, identified only as Beth. According to her claims, Agent X attacked her with a machete and leveraged his informant status to intimidate her into silence.

Beth brought her complaints to the oversight body responsible for monitoring MI5 conduct. In July, Deputy Investigatory Powers Commissioner Sir John Goldring published findings identifying “serious and systemic failings” by MI5 officers. His report detailed that one senior MI5 officer repeatedly lied, while another misled colleagues and provided false testimony regarding the handling of the case.

The controversy escalated when the BBC sought to report on the abuse allegations. Initially, MI5 acknowledged that Agent X was an informant to dissuade public exposure, citing concerns for his personal safety. However, during subsequent legal proceedings brought by Beth and the broadcaster, MI5 reverted to its usual policy, stating it could “neither confirm nor deny” any relationship with the individual.

In an unprecedented resolution, MI5 issued a public apology and compensated Beth, while the identity and nationality of Agent X remain undisclosed. He is believed to have left the United Kingdom.

Beth’s legal team is now urging the High Court to hold Sir Ken McCallum and the implicated MI5 officers in contempt of court. Such a ruling could carry penalties including imprisonment of up to two years or fines. Charlotte Kilroy KC, representing Beth, argued in written submissions that the deception was not the action of isolated personnel but rather a “sustained and long-lasting” pattern. Kilroy asserted that some MI5 officers knowingly obstructed justice by providing false evidence or failing to correct inaccuracies, and that the service as a whole benefitted from this misconduct.

Conversely, Tim Otty KC, counsel for MI5, contended there is “no basis” for attributing vicarious liability to Sir Ken McCallum and no strong case for corporate criminal contempt. He emphasized the agency’s commitment to reforms and stated that contempt proceedings were neither necessary nor appropriate at this stage.

The High Court panel has reserved judgment and will announce a decision on the matter in due course.