The Australian Federal Police and the federal department of finance have declined to confirm whether former speaker Peter Slipper offered to refund car-hire payments that are now subject to court action.
Investigative reporter Margo Kingston has reported online that Mr Slipper made the offer several months ago, before the AFP issued a summons for the Queensland federal MP to appear in the ACT Magistrates Court next month.
The summons document alleges that on three occasions in 2010, Mr Slipper took a hire car to visit wineries and restaurants as well as make trips within Canberra, to a value of $1194.
A source told AAP it would have been highly unusual for Mr Slipper not to have been given the chance to respond under the so-called "Minchin protocol".
The protocol, named after former minister Nick Minchin, requires that whenever an allegation is raised - whether through media or other sources - of misuse of parliamentary entitlements, the finance department considers it to ascertain if it is credible.
The member is sought for a response and the department may then recommend the MP repay any money they were not entitled to.
In the event of a serious allegation, the matter may be referred to a high-level departmental committee which can also seek an explanation from the MP.
If warranted, and on the advice of the secretary of the attorney-general's department, the matter may then be referred to the AFP.
When asked on Thursday by AAP to confirm whether Mr Slipper had offered to repay the money, the AFP declined to comment and referred the matter to the finance department.
A finance department spokesman said: "The department does not publicly comment on interactions between it and individual senators and members in relation to their entitlements."
However, the Minchin protocol did not apply where an allegation was referred directly to the AFP, the spokesman said.
Mr Slipper has yet to comment publicly on the matter but has hired prominent Brisbane lawyer Peter Russo, who made a name for himself representing Muhamed Haneef, the Indian doctor wrongly accused and charged by the AFP in 2007 for terrorist-related offences.
The veteran MP faces being stripped of his seat if convicted of any of the three charges.
The Australian constitution provides for an MP to be dismissed if they are convicted of "an offence punishable by imprisonment for one year or longer under a state or commonwealth law".
A senior source familiar with the rule told AAP that, given the maximum penalty for each breach of the Criminal Code Act is five years' jail, any penalty given to the MP would disqualify him from sitting in parliament.
Mr Slipper also faces losing hundreds of thousands of dollars in retirement benefits if convicted.
Currently he can expect a lifetime annual pension of about $157,000, but if convicted he could merely get a refund of his superannuation contributions without interest.
A resignation before the court action is concluded could protect his pension.
Mr Slipper has yet to say whether he will recontest his seat, which is expected to fall to Liberal National Party candidate and former Howard government minister Mal Brough.
A poll taken in mid-December by ReachTel gave Mr Slipper 2.7 per cent support, to Mr Brough's 48.4 per cent.
Ms Kingston wrote in an article posted on the Independent Australia news website on Thursday afternoon that sources had confirmed Mr Slipper had "immediately offered to repay the excess" when he was made aware of the overpayment.
"But sources say Finance refused to allow him to do this. Instead, they said that because the AFP was interested, they would not follow the (Minchin) protocol," Ms Kingston wrote.