Speaker Bronwyn Bishop won't be repaying money claimed for a trip in which she attended a Liberal Party colleague's wedding.
Mrs Bishop - who earlier this month agreed to pay back more than $5000 claimed for a helicopter charter to a Liberal fundraiser - claimed $600 for return flights from Sydney to Albury where she attended the wedding of former MP Sophie Mirabella in 2006.
Prime Minister Tony Abbott, who attended the same wedding, repaid $1100 in airfares, cars and allowances when the expenses were made public in 2013.
Mr Abbott's office said at the time he had been advised by the Finance Department it was not possible to determine whether the travel had been made within his entitlements.
However the Speaker's office told AAP on Tuesday Mrs Bishop would not be paying the money back because she was attending to business as chairwoman of the parliament's family and human services committee.
It is understood the business involved speaking on the Friday before the weekend wedding to witnesses wanting to give private evidence in the inquiry into work-life balance.
The rules allowed for chairs of committees to travel independently of other committee members without any specific approval, her office said.
Labor frontbencher Kate Ellis, who was on the same committee at the time, told reporters she struggled to see how it was committee business.
She called for Mrs Bishop to release details of the committee approval for the travel.
"We've seen the ducking and weaving but what we haven't seen is the black and white proof," Ms Ellis said.
The Department of Finance is currently reviewing Mrs Bishop's use of a hired helicopter to attend a Liberal fundraiser in Victoria last year.
The Speaker has agreed to pay back the cost of the trip, plus a penalty.
Acting Greens leader Larissa Waters said neither weddings nor party fundraisers were parliamentary business.
"It's about time MPs stopped rorting the system," Senator Waters said.
She said it showed the need for an independent commissioner to advise MPs on expenses.
Assistant Treasurer Josh Frydenberg said the Speaker had admitted her mistake with the helicopter and paid back the money.
"I think this is the politics of distraction," he told Sky News.
An Essential poll found only 19 per cent of voters believed she should remain as Speaker, and 25 per cent said she should step aside pending the investigation.
A further 19 per cent want her to resign as Speaker and 24 per cent think she should quit parliament entirely.
