A Senator who once tried to smuggle a knife into the New South Wales Parliament has warned planned security cuts at Federal Parliament could allow mischievous people to bring unwanted items into the building.

Long-time Liberal Senator Bill Heffernan says he is deeply concerned at possible budget cuts which would see security at the Parliament building in Canberra relaxed.

The ABC understands the number of security personnel guarding the perimeter of Parliament will soon be reduced, and X-ray screening of some items will no longer happen.

"If the Australian Federal Parliament can't afford, due to budgetary restraints, to have the security that we now have, then we ought to shut the building down," Senator Heffernan told the Upper House on Wednesday night.

"Because if you can't secure the perimeter of the building then why the hell would you worry about the internal security?"

Senator Heffernan says forbidden items could get past security.

"If a person's got something in their mind of a mischief nature then you would be able to get it into Parliament," he said.

The outspoken Senator has pleaded with the Finance Department to rethink any cuts to the Parliamentary security budget.

"There's got to be a better way to manage the security of this building due to budgetary restraints than getting rid of some of the security as you enter the building" he said.

In March 2009 Senator Heffernan apologised for threatening a security guard who had confiscated a knife from him at New South Wales Parliament House.

At the time Senator Heffernan allegedly claimed he was testing security during a visit to NSW Liberal MPs.