Prime Minister Tony Abbott has repaid more than $1,000 in taxpayer-funded travel expenses he claimed when he attended a wedding.

In Opposition the Coalition was scathing about other MPs who were investigated over their travel expenses.

Now Mr Abbott has paid travel costs he claimed to attend the wedding of former colleague Sophie Mirabella in 2006.

A spokeswoman for Mr Abbott says the money was reimbursed because the Finance Department is not sure the trip was within his entitlements, and he wanted to avoid any doubt.

Communications Minister Malcolm Turnbull says the rules can be ambiguous, telling the ABC's Insiders program it is "not uncommon to pay expenses claims back".

Mr Turnbull also defended other Coalition colleagues who are facing questions about their travel claims.

In 2011 mining billionaire Gina Rinehart flew then opposition frontbenchers Julie Bishop, Barnaby Joyce and Teresa Gambaro to a wedding in India.

All three claimed overseas study entitlements for the trip home.

Ms Bishop says the primary purpose of her visit was to meet with Indian companies, while Ms Gambaro detailed her visit to an international development program.

Mr Joyce says he went on from the wedding to Malaysia for official meetings.

Mr Turnbull says the entitlements register is not always clear.

"The better course of action is to err on the conservative side and if there's any doubt, then don't make a claim, but all of the colleagues you've mentioned are people that are scrupulous about how they use taxpayers' money," he said.

Mr Turnbull says the expenses Ms Bishop claimed "sounded like a very valid use of her travel entitlement because of all the business engagement she made".

"It sounded to me... that Julie Bishop's visit to India was very much in line with what she should have been doing as shadow foreign minister," he said.

Last month Mr Joyce denied any wrongdoing after reports said he used taxpayer funds to attend a different wedding.

Fairfax Media reported both he and Coalition frontbencher George Brandis claimed travel expenses to attend the nuptials of radio presenter Michael Smith in 2011.

Senator Brandis confirmed he claimed nearly $1,700 on flights, accommodation and a hire car, but says he attended the wedding primarily for work purposes.

He later wrote a letter to the Finance Department with a cheque for the costs, saying he would pay them to "resolve any uncertainty" about the issue.

Mr Joyce rejected the Fairfax report, saying he may have used a Commonwealth car on the day, but he did not claim flights or accommodation.

Labor remain concerned about validity of entitlement claims

Acting Labor leader Chris Bowen says there are still questions that must be answered.

"This simply isn't good enough. The Australian people deserve full transparency and disclosure here," he said.

"I call on Mr Abbott and Mr Brandis, instead of saying that these claims were legitimate and they're paying them back in order to avoid any doubt, to actually admit they got it wrong.

"To admit that this is an illegitimate claim, this is a breach of the guidelines.

"Mistakes happen... but I think the Australian people are entitled to expect their politicians to be honest about when mistakes happen and give them an honest explanation.

"This goes to judgment of senior Liberals. Claiming travel expenses for what are very clearly not legitimate travel expenses."

According to the federal Department of Finance and Deregulation's entitlements handbook, expenses for official business such as "meetings of a government advisory committee or taskforce" or "functions representing a minister of presiding officer" are allowed for.