The Secretary of the Department of Parliamentary Services has confirmed it was “human error” that saw a major security breach at Parliament House and pose a potential threat to the Prime Minister.

Appearing before the Senate Finance and Public Administration Committee during Supplementary Estimates, Secretary Carol Mills said CCTV had confirmed a man known to parliamentary security had wondered through an unguarded access door into the private areas of Parliament House.

Ms Mills told the hearing the intruder remained in the building for 40 minutes, all that while unnoticed by security staff as he visited the office of the Deputy Prime Minister, the Speaker and another MP.

The office of the Deputy Prime Minister alerted parliamentary security services to the presence of the intruder, but in the two minutes it took for security personnel to reach the intruder, he had breached the Prime Minister’s press conference, handing her a document. It was only at this point that Parliament House security caught up with the intruder

“By definition, the security system at Parliament House broke down,” Senator Ryan, deputy chair of the Senate Finance and Public Administration Committee said. “It is ridiculous that an intruder, who was brought to the attention of parliamentary security only days before, was subsequently free to wander the building and approach the Prime Minister.”

“It is just lucky that on this occasion, the intruder’s motives were not more sinister. I hope the Government encourages the department to make security at Parliament House its highest priority.”

Ms Mills said the intruder had been known to Parliament House staff, having interrupted a public committee hearing 10 days before the security breach. A photo had been circulated to security staff stationed at a follow up committee hearing, but Mr Naumov did not attend.

Ms Mills said while her department responded straight away, she was not informed until 90 minutes after the incident. She commissioned a $30,000 report into the security breach, led by former NSW bureaucrat Carolyn Walsh As a result of the report, security procedures have been altered to prevent a similar incident.

Asked by Senator Ryan whether she was confident a similar incident would not happen again, Ms Mills said rostering changes, more back-ups and better communication between the Department of Parliamentary Services and the Australian Federal Police had been put in place.