Scott Morrison says he has ordered an internal investigation into claims his media team “backgrounded” journalists with negative information about the partner of Brittany Higgins, shortly after she made a formal complaint to his chief of staff.

Ms Higgins’ letter to Dr John Kunkel, the PM’s right-hand-man, came on Thursday after Scott Morrison essentially challenged her to do so.

“I would like to make a formal complaint as per the Prime Minister’s directives on ABC AM with Sabra Lane this morning,” she wrote.

The Prime Minister had consistently dodged more than a dozen questions in Parliament about the explosive claims – made by Ms Higgins’ in her powerful speech to Canberra’s March 4 Justice – that his office gave negative information to journalists, following her allegation she was raped inside Parliament House in 2019.

However, on Thursday, he confirmed he’d received the letter from Ms Higgins, as well as further “confidential information” from a “primary and direct source”.

“In response to that information, I have asked my chief of staff to commence a process with advice from the Department of Finance to deal with complaints against staff members,” Mr Morrison said in Question Time.

He also committed to responding to Ms Higgins’ letter.

Earlier on Thursday morning, when asked in an ABC radio interview about the claims of backgrounding, Mr Morrison said that “no one … has raised that with my chief of staff”.

Hours later, Ms Higgins took up the challenge herself, writing a formal letter to Dr Kunkel.

Ms Higgins’ letter to the Prime Minister’s chief of staff.

“I believe in giving people the benefit of the doubt. It is entirely plausible the Prime Minister did not know this was happening. However, the more relevant point is that it did occur,” Ms Higgins wrote of the alleged backgrounding.

“To my knowledge, this was being done by staff within the Prime Minister’s media team.”

After Ms Higgins’ rape allegations became public in February, several journalists in the Canberra press gallery claimed the PM’s office had “backgrounded” selected reporters with negative information about Ms Higgins’ partner.

The claims were shared in a Radio National interview by Channel 10 political editor Peter Van Onselen, and then reported in major national publications. Ms Higgins also called it out in her speech to thousands, on the front lawn of Parliament on March 15.

In her letter, Ms Higgins claims “multiple journalists” at News Corp and Channel 10 told her about “the backgrounding that was happening against my partner”, following her public allegations of rape by a colleague in a ministerial office.

Ms Higgins also told Mr Kunkel she wanted to participate in the investigation by Department of Prime Minister & Cabinet secretary Phil Gaetjens into what Mr Morrison’s office knew about the alleged rape. That internal investigation was paused two weeks ago, while federal police also investigate the rape claims.

Ms Higgins’ letter puts further pressure on Mr Morrison to further investigate the claims of backgrounding by his staff, after days of shrugging off similar questions from Labor.

Brittany Higgins accused the PMO of “backgrounding” against her partner. Photo: supplied

Last week, Ms Higgins told the March 4 Justice that she had “watched as the Prime Minister of Australia publicly apologised to me through the media, while privately his media team actively undermined and discredited my loved ones”.

For seven parliamentary sitting days in a row, opposition MP Catherine King has asked Mr Morrison if his office did background against Ms Higgins. The PM has repeatedly dodged the question, saying only he is unaware of any backgrounding.

“I’ve no knowledge of that and I would never instruct that. I would never instruct such a thing. I would never do that. The apology that I offered in this place to Brittany Higgins was sincere and was genuine, and I’m happy to restate it,” he said last Monday, in response to Ms King’s first question.

Ms King has asked a dozen more times since then. On Monday, Mr Morrison said “there’s no information before me to suggest any of these things have occurred”.

However, as Labor pointed out, he has not said if he has asked his media staff about the claims – only that he has not been presented with such information.

On the alleged backgrounding, Mr Morrison told the ABC on Thursday that “people make allegations all the time second, third-hand”.

“There has been no one in the gallery, nothing has been raised with my office from anyone in the gallery making any of those accusations or any discomfort about anything that my office has done,” he said.

“She [Ms Higgins] did a great job when she was working for the Coalition and I thank her for all the great work she did.”

The New Daily understands that some journalists have raised concerns about the alleged backgrounding with PMO staff.