The Commonwealth law enforcement integrity agency will investigate how police investigators handled Brittany Higgins’ rape allegation.

The ACT Director of Public Prosecutions Shane Drumgold raised concerns about “political and police conduct” in the case of former political staffer Bruce Lehrmann, who Ms Higgins alleged raped her in Parliament House in 2019.

Mr Lehrmann denies the allegations.

ACT Attorney-General Shane Rattenbury confirmed the matter had been referred to the Australian Commission for Law Enforcement Integrity for further investigation.

“I am aware the matter has been referred to the Australian Commission for Law Enforcement Integrity. As such, it is not appropriate to comment further at this time,” he said in a statement.

The police union earlier slammed Mr Drumgold’s office for criticising the Australian Federal Police and ACT Policing who investigated the matter.

In a statement, Australian Federal Police Association president Alex Caruana said the union “wholeheartedly” supported a judicial inquiry into Mr Lehrmann’s trial.

But he said “desperate attempts” to smear the police forces by the territory’s top prosecutor were untested and the subject of an internal investigation.

In a document revealed under freedom of information laws, Mr Drumgold wrote police had engaged in a campaign to pressure him not to prosecute Mr Lehrmann over Ms Higgins’ allegation.

On Thursday, The Guardian reported Mr Drumgold sent a letter to the ACT’s police chief, Neil Gaughan, on November 1 outlining concerns over police conduct.

“I am of the view that at the conclusion of the trial, there should be a public enquiry into both political and police conduct in this matter,” Mr Drumgold wrote.

But Mr Caruana said the union “firmly believes” the ACT DPP compromised Mr Lehrmann’s trial.

He said any inquiry must also assess the conduct of Mr Drumgold, his office, the ACT Victims of Crime Commissioner and Mr Rattenbury.

He also questioned whether the information obtained by The Guardian had been deliberately leaked by Mr Drumgold’s office.

“The FOI from the ACT DPP to The Guardian, to our knowledge, has no redactions, and it includes personal details of officers involved in the investigation,” he said.

“ACT Policing was not consulted on the release of information and its members’ details.”

ACT Policing said it was aware the Office of the Director of Public Prosecutions had released the letter and noted the DPP had requested a public inquiry into the matter.

“As such, it would be inappropriate to provide any further comment in relation to any aspects surrounding this matter including commentary about the letter from the ACT DPP,” a spokesman said on Thursday.

Mr Caruana said the union intended to make a formal complaint to the Australian Information Commission and the ACT Ombudsman about the possible FOI breach and alleged “misconduct by the Director of Public Prosecutions”.

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– AAP