Despite the Prime Minister making the personal decision to repay the money, the emails suggest Mr Abbott could not rely on the Finance Department to provide guidance. Most revealing was an email, dated October 5, 2013, sent from the Department of Finance to the Department of Prime Minister and Cabinet. "Mr Abbott's claim for the June 2006 travel to Albury was claimed as official business as a minister," the email states. "Finance has become aware that the travel coincided with the wedding of a parliamentary colleague – Ms Sophie Mirabella." The email goes on to say that Finance does not have "access to the paperwork today ... as it is held in archive".

"On the basis of the information available it is not possible to determine whether the travel was made in accordance with the relevant determination," the email concludes. The FOI request was submitted by citizen journalist Margo Kingston, who said she ''crowdfunded'' the payments for the request. The failure of the department in charge of MP entitlements to provide a ruling follows a pattern in which it has been unwilling to comment or take action on any of the examples of questionable travel claims revealed by Fairfax Media. And it comes as the Australian National Audit Office interrogates the "effectiveness of the Department of Finance's administration of travel entitlements provided to parliamentarians". In recent months, the Finance Department has refused to say whether it would examine allegations that former Coalition MP Alex Somlyay employed his wife for non-existent "electoral office" work.

Nor, according to West Australian MP Don Randall, could the Finance Department enlighten him on whether his overnight trip to Cairns with his wife in 2012, which coincided with the couple taking possession of an investment property, satisfied the description of "electoral business". Mr Randall has since repaid more than $5000 he charged taxpayers for the Cairns trip. Fairfax Media sent a number of questions to the Finance Department on Thursday, asking why it was unable to determine whether Sophie Mirabella's wedding constituted "official business". The Finance Department's response illustrates limitations of the "honesty system" that leaves it up to politicians to decide on their own expenses and which some believe has led to inadequate policing of MPs' entitlements. "The entitlements framework is purpose based and the purpose of the travel is determined by the Senator or Member," a Finance Department spokeswoman replied. "The department does not approve travel... The department cannot determine for a parliamentarian if an event they are attending is official or electorate business."

The parliamentarian must satisfy themselves that their travel is within the entitlement stated within the Parliamentary Entitlements Framework." During the expenses scandal last year, Mr Abbott also repaid $609 he spent travelling to the Brisbane wedding of former Coalition colleague Peter Slipper. But the new emails released under FOI show the taxpayer-funded travel costs for Mr Slipper's wedding totalled $1899. Mr Abbott's office would not comment on the $1200 discrepancy between the payments, but a Finance Department email suggests "Mr Abbott undertook official functions on that trip that weren't related to the wedding". Follow us on Twitter