Prime Minister Tony Abbott has dodged questions about whether Speaker Bronwyn Bishop should repay a taxpayer-funded trip to a colleague's wedding, despite having repaid the cost of travelling to the same wedding himself.

Fairfax revealed on Friday Mrs Bishop claimed $600 for a return flight to Albury to attend the wedding of Liberal colleague Sophie Mirabella in 2006.

The Speaker, already "on probation" for taking a helicopter to a party fundraiser, is refusing to pay the money back, and is refusing to provide details of what "official business" she conducted on the trip. This is despite Mr Abbott already having repaid $1000 in entitlements to travel to the same wedding two years ago when he urged colleagues to follow his example.

When asked whether Mrs Bishop ought to repay the cost of the taxpayer-funded travel, the Prime Minister declined to either answer directly, or defend Mrs Bishop's actions.

"This is, I think, something that has been quite properly looked at by the Department of Finance," Mr Abbott said. "I'm confident that in the wake of this particular issue, everyone in public life, certainly every member of Parliament, well and truly understands that our dedication has got to be constantly to the people of Australia."

Labor MP Pat Conroy said Mr Abbott's comments showed he was not punishing Mrs Bishop, often described as his political mentor.

"Tony Abbott ... repaid the money claimed to attend this wedding because it's obvious the taxpayer should not be paying for this," Mr Conroy said.

"She should have resigned weeks ago, and the longer this goes on the more it shows that the Liberal Party and Tony Abbott are out of touch."

Mr Abbott, too, sought advice from the Department of Finance in 2013, before repaying more than $1100 in travel costs and travelling allowance to attend Mrs Mirabella's nuptials.

But the department declined to give him an official ruling on whether travelling to a colleague's wedding amounted to official, electorate or parliamentary business.

Mr Abbott then repaid the money of his own volition "for the avoidance of any doubt" about whether such travel is legitimate.

When he repaid the money, the Prime Minister issued a warning to a party room being enveloped by an expenses scandal to follow his lead and repay any doubtful expenses.

A spokesman for Mrs Bishop told Fairfax Media she was on "official committee chair business" on the trip, but declined to provide further details at the time.

The same explanation was provided to the federal government, in documents lodged in Mrs Bishop's own handwriting.

In 2006, the year of the wedding, Ms Bishop was the chairwoman of the standing committee on family and human services.

The Speaker's office has refused to provide details of what official business Mrs Bishop conducted on the trip to Albury and initially declined to comment to Fairfax altogether.

A spokesman later reportedly told other outlets that the committee in question was holding an inquiry into "work-life balance" and that it was not uncommon for committee chairpeople to conduct their own research into issues.

The standing committee held no official meetings, or hearings in Albury that year.

Betty Collins, a former long-serving secretary of the Commonwealth Remuneration Tribunal, which sets rules governing MP entitlements, last week told Fairfax that MPs could only claim for committee travel to official, organised and documented meetings.

Mrs Bishop travelled about an hour from Albury to Wangaratta for the wedding and back.

The Speaker was last week forced to repay more than $5000 and a $1300 penalty for chartering a helicopter to attend a party fundraiser.

A Department of Finance spokesman said the department "does not comment on its dealings with individual parliamentarians".

Follow us on Twitter