Prime Minister Malcolm Turnbull is being called on to back an investigation by the Australian Federal Police into revelations about misuse of former treasurer Joe Hockey's Cabcharge account.
Greens Senator Lee Rhiannon made the demand after Fairfax Media revealed the rules for MPs using privately chauffeured hire cars were repeatedly broken in relation to Mr Hockey's Cabcharge account during his time as shadow treasurer.
Documents obtained under freedom of information laws show drivers from a favoured hire car company - Ecotaxi, owned by former policemen Russell Howarth - filled out and signed on Mr Hockey's behalf Cabcharge dockets worth at least $10,000 from as early as 2009.
Many of the dockets – for amounts as high as $760 each at $95 an hour - do not contain destination or time details, but simply state the driver transported Mr Hockey "as directed" for up to eight hours at a time.
Some show Mr Hockey's Cabcharge account, details of which were hand written by the driver on the docket instead of being "embossed" with card details, had expired before the date of the trip.
They showed Cabcharge proposed in April 2012 to refer the "apparent fraud" to the Australian Federal Police, inviting Mr Hockey to speak directly to Cabcharge boss Reg Kermode.
Shortly afterwards Mr Howarth signed a statutory declaration saying Mr Hockey had no knowledge of the process and that all trips were genuine and his office had previously urged him to correctly invoice for them.
Mr Hockey says he has "no recollection" of speaking to Mr Kermode, who died in 2014 and Cabcharge has declined to comment on whether he did.
Cabcharge did not proceed with a police referral as it says the issue was "resolved" with the Department of Finance.
But Senator Rhiannon said: "As this case involves possible fraud there is a clear case for Mr Hockey's hire car habits to be investigated by the Australian Federal Police".
"Considering how the former treasurer and his colleagues quickly referred the former speaker Mr Peter Slipper to the AFP the same rules should apply in this latest scandal," she said.
Cabcharge wrote to Mr Hockey flagging a referral to the AFP as Tony Abbott's opposition pursued then speaker of the House of Representatives, Peter Slipper.
A former staffer had alleged Mr Slipper had misused his Cabcharge entitlements by handing over blank but signed Cabcharge dockets for drivers to fill out.
Mr Slipper was convicted in 2014 of three counts of dishonesty over misuse of about $900 worth of Cabcharge entitlements to visit wineries. The convictions were overturned on appeal.
Mr Howarth has told Fairfax Media that all the trips taken by Mr Hockey with his company were "above board" and for official business.
Mr Hockey said Cabcharge and Mr Howarth sought to "embroil him" in their dispute over the dockets.
He said he ceased using Mr Howarth's services after the matter was resolved.
"Every paid receipt was matched with appropriate travel," he said.
Mr Hockey is Australia's ambassador to the United States.
