Labor is demanding Tony Abbott explain why he hosted two private parties for a high school reunion and final staff farewell at Kirribilli House days after being deposed as Prime Minister.

Mr Abbott on Friday night held drinks for more than 50 of his old Riverview classmates. He greeted each of the former students at the door to the prime minister's official Sydney residence - Kirribilli House. The class of '75 arrived in two buses.

It has been reported that the event was privately funded and will raise money for charity. Kirribilli House can be used for charitable fundraising.

News Corp on Monday reported Mr Abbott held a second party for his staff on the weekend. Guests included his chief of staff Peta Credlin, deputy chief of staff Andrew Hirst and the junior advancer Richard Dowdy who infamously welcomed Mr Turnbull into the top job last Monday with an unprintable four-letter expletive.

Labor MP Pat Conroy has written to the Department of Prime Minister and Cabinet, demanding an explanation as to why Mr Abbott was allowed to use the prime minister's residence for both events.

"I am writing to clarify if the use of an official residence for a private school reunion is an appropriate use of this residence," Mr Conroy wrote in a letter to departmental secretary Michael Thawley.

"The Member for Warringah is a backbench Member of Parliament and does not have an entitlement to entertain at Kirribilli House," the Member for Charlton wrote.

Mr Conroy noted that Prime Minister Malcolm Turnbull could have granted Mr Abbott permission to use Kirribilli House but said that "would be inconsistent with longstanding practice".

Mr Conroy listed six questions he wants the Department to answer, including whether any taxpayer-funded staff helped organise the events, whether authorisation was sought and granted and who paid for the clean-up, and if all MPs and senators can apply to use the residence for a school reunion.

Mr Abbott's office was contacted for comment.

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