The head of Parliament House's security branch has admitted he might have said he would "burn the security division to the ground and start again with other people".

Key points: DPS head "can't recall" comment about burning DPS to the ground, but says if he did it wasn't intended as a threat

DPS head "can't recall" comment about burning DPS to the ground, but says if he did it wasn't intended as a threat He denied a request for a senior security officer to give evidence about the white powder incident, and denied telling another not to ring AFP about it

He denied a request for a senior security officer to give evidence about the white powder incident, and denied telling another not to ring AFP about it DPS secretary says morale is being damaged and confidence undermined by leaks within the security branch

Graeme Anderson made the extraordinary admission while being questioned in a Senate Estimates committee on Monday.

He said he "apparently" might have made those comments and described it as "[sounding like] something I might have said".

The exchange reveals the extent of tensions over security in Parliament House, which has also seen a sensitive operating manual leaked to the media and concerns raised about the handling of suspicious white powder.

Secretary of the Department of Parliamentary Services (DPS) Rob Stefanic also revealed there were divisions between security staff.

He said leaks to the media had prompted some guards to complain to him about their colleagues.

"In recent days I have been approached by a number of security staff that are expressing their dismay and disappointment about the behaviour of the small number of anonymous colleagues who continue to misrepresent information about our security operations in a deliberate attempt to mislead and misinform journalists and senators," Mr Stefanic said.

"These leaks are calculated to generate publicity and create the false impression of the security operation that may undermine public confidence in the security of Parliament House."

AFP could investigate security leaks from inside Parliament

Mr Stefanic said the adverse publicity also had a significant impact on staff morale.

He told senators he had asked Australian Federal Police (AFP) Commissioner Andrew Colvin about an investigation into the security breaches.

Some of the recent leaks relate to an incident last November, when Mr Anderson used his finger to taste a suspicious lump of white powder to confirm it did not pose a safety threat to the building.

Mr Anderson has previously defended his handling of the incident as exactly as it would have been had he still been in the AFP.

But many Parliament House guards remain bewildered by their boss's actions.

This suspicious lump of white powder was found near the public cafe last November. ( Supplied )

Labor senator Kimberley Kitching said another very senior security officer was not allowed to give evidence at Estimates on Monday.

She said she asked for the assistant director of security operations, Michael O'Mahony, to appear before the committee because he had "unique knowledge" of that white powder incident.

But she said the department had refused to allow him to appear.

Senator Kitching asked Mr Anderson whether he stopped Mr O'Mahony from contacting the AFP to report the white powder incident when it happened last November.

Mr Anderson denied that.

"Absolutely not, Senator. I don't know where that has come from but it is categorically false," Mr Anderson said.

He told Senator Kitching that Mr O'Mahony had twice tried to phone the AFP but the calls were unsuccessful.

Comments about burning DPS to the ground 'not threats'

Senator Kitching put the claim to Mr Anderson that on a number of times he had said: "I'll burn this security division to the ground and start again."

He said he did not recall making the statement but, if he had, he was not referring to people but instead the issues that "need correcting within security branch".

Labor's Senate leader Penny Wong indicated she thought security staff would have regarded the remark about burning the division to the ground as a threat.

Mr Anderson said it was not intended that way.

Senate President Scott Ryan said the security environment had changed quite dramatically in recent years and that could be "quite confronting" for staff.

"This is an area of some challenge within the Department of Parliamentary Services," Senator Ryan said.

There are reports about security officers being issued with cheap disposable painting overalls to wear while conducting tests on suspicious white powder delivered to the Prime Minister's office.