''The protocols were never intended or designed to be a mechanism to 'let MPs off the hook' and it does provide for departmental officials to refer allegations to the federal police where that is deemed appropriate,'' Mr Minchin reportedly said. Refused to commit to changes to the parliamentary expenses system: Prime Minister Tony Abbott. Credit:Alex Ellinghausen West Australian state Liberal MP Rob Johnson called on Mr Abbott to dump the embattled federal WA Liberal Don Randall over a taxpayer-funded trip to Cairns with his wife in November last year. That cost the public $5259 and has not been explained beyond the two words ''electorate business''. In a statement on Thursday Mr Randall said he would immediately reimburse the full cost of the trip to ''ensure the right thing is done by the taxpayer and alleviate any ambiguity''.

''I today contacted the Department of Finance seeking urgent advice in relation to my Cairns travel expenses due to the ongoing media scrutiny and public interest about this matter," he said in the statement. Attorney-General George Brandis. Credit:Sasha Woolley "The Department informed me that it cannot provide definitive advice.'' The decision comes after days of refusing to respond to requests from Fairfax Media to specify the nature of the so-called ''electorate business'' in Cairns. It appears to reflect an open admission that the original claim was not capable of being defended on the very basis it was made.

However, Mr Randall continued to claim that the trip was bona fide even though he has provided no additional information, and had decided of his own volition to repay the money rather than defend the claim. ''I've always acted in good faith when submitting claims and after an extensive review of all my expenses, I’m satisfied that those claims meet the guidelines,'' he said. The Randalls took possession of an investment property in Cairns at the time, a fact recorded in the parliamentary register of members' financial interests just a week after the Cairns visit. With the scandal dominating politics, Victorian Labor MP Rob Mitchell revealed on Thursday he had written to the AFP seeking a formal investigation of claims by Mr Abbott and Senator Brandis to attend the weddings of Peter Slipper and Sophie Mirabella. Mr Mitchell said there appeared to be ''a consistent and deliberate abuse of taxpayer funds for personal gain''.

NSW Nationals senator John Williams also called on Mr Abbott to tighten the system, saying people who were struggling with the cost of living were annoyed to see stories about politicians' expense claims. ''The Australian people must have faith in a government and all politicians that we're doing the right thing,'' Senator Williams said. With the government bleeding over the Randall case, one of a string of expenses scandals on both sides of politics, Mr Johnson branded Mr Randall ''a coward'' and said he was speaking up on behalf of other ''disgusted members of the WA party''. ''He should resign from Parliament or the Prime Minister should show some leadership and sack him,'' said Mr Johnson, a former state minister and current member of the Barnett government. He said Mr Randall needed to explain to his constituents exactly what business he was doing on their behalf on trips to Cairns and Melbourne with a family member.

Mr Johnson acknowledged that the pair ''had history''. Mr Abbott has so far refused to commit to changes to the parliamentary expenses system, despite multiple cases of MPs making false claims that, if made in a tax return, could lead to prosecution. Mr Abbott's chief of staff Peta Credlin this week told all Coalition MPs to get approval from the Prime Minister at least four weeks before travelling overseas. Monday's email said MPs and senators were ''reminded that approval must be sought'' for overseas study travel, sponsored travel and privately funded trips, but not for parliamentary delegations. It followed Fairfax Media reports on Coalition MPs Barnaby Joyce, Julie Bishop and Teresa Gambaro flying to India on a private jet funded by Gina Rinehart to attend a wedding, then claiming ''overseas study'' entitlements to cover the cost of the return journey.

A spokesman for the Special Minister of State Michael Ronaldson dismissed the referral to the AFP as ''a political stunt''. Loading ''I trust Rob Mitchell has also written letters to the Federal Police asking they investigate Tony Burke, Julia Gillard, Anthony Albanese, Mark Dreyfus, Jacinta Collins, Senator Mark Bishop, Senator Don Farrell, Trish Crossin and Kirstin Livermore,'' he said. The AFP announced on Thursday that it would not be investigating the alleged misuse of MPs entitlements, despite the multiple complaints, but had forwarded them to the finance department.