Australian Federal Police Commissioner Reece Kershaw wrote to MPs and senators in February about the need to report crimes after former Liberal staffer Brittany Higgins went public with rape allegations.

At a Senate estimates hearing in Canberra on Tuesday, Mr Kershaw said the letter resulted in 40 reports about potential offences linked to politics.

He later clarified not all were sexual offences but confirmed some of them did relate to potential crimes in that category.

"Some of them are quite sensitive and difficult so we've been able to provide advice and assist with what the correct process is," Mr Kershaw told the committee.

The AFP commissioner said some of the submissions involved allegations against politicians and staff.

"That's why we have to handle all these matters sensitively, because they are allegations."

A dozen of the reports have been marked as sensitive investigations, while a further 10 have been referred to state or territory police.

The AFP has finalised its investigation into one matter, while another is the subject of ongoing inquiries.

Mr Kershaw said seven did not relate to electorate officers, ministerial staff or official establishments.

Officers were unable to say how many were about incidents that happened within Parliament House and took questions about whether any MPs were being investigated on notice.

Ms Higgins says she was raped by a colleague in a minister's office while employed as a staffer in March 2019.

After investigating the allegations, ACT police are expected to refer a brief of evidence to prosecutors within weeks.

Australian Associated Press