But officials could not immediately say whether the malfunction was responsible for lights being on in Climate Change Minister Penny Wong's office.

Senator Wong was criticised after her office remained lit up between 8-9pm on March 29 for Earth Hour a worldwide event to combat global warming. She defended her staff, saying the only lights on were those controlled by building management.

Most of Parliament House was in darkness for the hour.

Department of Parliamentary Services officer John Nakkan confirmed that a technical glitch turned lights and air-conditioning back on in several ministerial suites.

''The outer row of lighting adjacent to the windows is automatically controlled by the building management system. The general lighting in the suites are controlled by switches on the walls,'' Mr Nakkan told the committee.

''We did have a malfunction at the time on several offices in the building management system the lighting and the air-conditioning.

''There were several in the ministerial wing.''

Mr Nakkan could not say whose offices were affected, prompting Liberal senator Mitch Fifield to query whether Senator Wong was trying to escape blame.

''I'm just wondering whether Senator Wong, who understandably as the Minister for Climate Change would be acutely embarrassed to have her office illuminated during Earth Hour, whether she is trying to blame the department for something which was within the control of her office or, if as you say, there was a malfunction of some sort,'' he said.

''We'd all like to see the Climate Change Minister practise what she preaches ... I don't want to be in any way, shape or form cynical, but it would seem to be extremely convenient for the ministers concerned that there was a malfunction affecting their suites on the night of Earth Hour.'' AAP