The Australian Federal Police has received a letter alleging that Liberal MP Mal Brough admitted to a crime on national TV.

A federal Labor MP has written to the Australian Federal Police asking them to investigate government backbencher Mal Brough.

Graham Perrett believes Mr Brough may have committed a crime by obtaining a copy of former Speaker Peter Slipper’s diary.

Mr Brough, a former Howard government minister, told the Nine Network he had directed Mr Slipper’s adviser James Ashby to procure copies of the diary in 2012 for his use.

At the time, Mr Brough was preparing an ultimately successful Liberal preselection bid for Mr Slipper’s Queensland seat of Fisher, which he won at last year’s election.

Mr Perrett, a Brisbane-based Labor MP, said this admission showed Mr Brough may have breached the commonwealth criminal code or the Crimes Act of 1914 through his unauthorised access to the data.

“That conduct could constitute a serious crime,” the shadow parliamentary secretary wrote in a letter to AFP Commissioner Tony Negus.

Mr Perrett said Mr Brough’s admission on Sixty Minutes on Sunday was new evidence.

Fellow Labor MP Michael Danby has asked the Commonwealth Director of Public Prosecutions to investigate whether Mr Ashby committed perjury by contradicting a Federal Court affidavit that he had not been promised any financial help to launch a legal case against Mr Slipper, in his Sixty Minutes interview.

But Mr Perrett was less eager to pursue Mr Ashby.

“Apart from the disparity between his affidavit and his statements to Liz Hayes (on Nine), there did not seem to be any clear admission of a crime,” he said.

“Mr Ashby has been through a pretty difficult set of circumstances. He wasn’t an experienced minister like Mr Brough.”

The AFP confirmed it had received a letter about the alleged unauthorised disclosure of the diaries but declined to comment further.

“The AFP is evaluating the matter,” it said in a statement.

Mr Brough declined to comment on Mr Perrett’s letter.