LONDON (AP) — The British government said Thursday it will keep the country’s spies on a tighter rein after a report found MI5 misled courts about its ties to a neo-Nazi informer accused of attacking his partner.

Home Secretary Shabana Mahmood said she is taking “urgent action” to strengthen oversight of the U.K.’s domestic security service after a tribunal found MI5 repeatedly gave “a false account” of what had happened.

Earlier this year MI5 apologized and paid compensation to settle a legal claim brought by a woman over her treatment by an allegedly abusive ex-partner. He was an MI5 informant, identified in court as Agent X.

MI5 maintained in sworn testimony that it had neither confirmed nor denied that Agent X was an informant. But in fact an MI5 officer had disclosed the information during a conversation with a BBC journalist who was investigating Agent X.

The Investigatory Powers Tribunal, which investigates allegations against Britain’s intelligence services, said MI5 had misled three courts because a false narrative was “allowed to take hold and persist.” It said “systemic failures” meant chances to correct the error were missed,

“The findings of this report are stark. It details serious failings by individual MI5 officers, resulting in false evidence being provided to the courts, and criticism of MI5 as an organization,” Mahmood said.

“MI5 plays a critical role in keeping our country safe and we owe a debt of thanks to its staff. They have made significant progress over the last year in learning from these failures, but there is more to do to ensure the highest standards of integrity and accountability are upheld.”

MI5 Director-General Ken McCallum said the agency “recognizes without hesitation the seriousness of our failings” and was working “to ensure we never find ourselves in this position again.”

In a separate case last year, a report found that MI5 protected a top spy planted within the Irish Republican Army when they knew he was wanted by police for murder, and continued to suppress the truth about the agent decades after Northern Ireland ’s bloody conflict.