Liberal senator Bill Heffernan has taken a mocked-up "pipe bomb" into Parliament House to show new security arrangements are "a joke".

Under the new system, some passholders and their belongings are not scanned when entering the building.

Previously, everybody coming into Parliament House had to be checked through security.

Senator Heffernan says the building is "no longer secure".

"To demonstrate that, this morning, I brought in what could be... I brought this through security - a pipe bomb," he told a Senate Estimates hearing, as he held up a metal pipe.

He also held up what appeared to be an electronic device.

"When I was a kid, we used to blow stumps out on the farm - 50 years ago," he said, detailing the ingredients for his home-made bombs.

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"We could blow a tree the size of this building out of the ground.

"At the present time, there is nothing to stop anyone from bringing those ingredients in here over a period of time through security."

Australian Federal Police Commissioner Tony Negus, who is appearing at the committee, said: "That is a risk, yes".

Senators from both major parties have raised concerns about the new guidelines, which allow members of parliament, their staff , family, and staff of parliamentary departments to walk through the entrances without being checked.

Senator Heffernan says passholders still pose a danger, even if they have security clearance.

"The big weakness ... is the risk of people who might be subject to compromise," he said.

"And I could take you through endless examples of that."

His partyroom colleague, LNP Senator Ian Macdonald, interrupted, saying: "We just hope you're not doing anything illegal to which we are accessories".

Mr Negus said the AFP had been in "regular consultation" with parliamentary officials about what it believed was an "appropriate level of security".

"Those elements are being considered," he said.

The AFP chief later told the committee Senator Heffernan had warned him he intended to use the pipe as a prop.

"It was just a piece of pipe. He did show me that piece of pipe this morning, before I walked in, and said he was going to use it in some sort of demonstration," he said.

"I was satisfied it was inert, that it was metal pipe and that's all it was."

The committee heard one of the reasons behind the change in security arrangements was to save money.

A statement from the Department of Parliamentary Services, emailed to building occupants earlier this month, explained the changes were being trialled and were in line with other parliaments in Australia.

It said the trial would be reviewed early next year.