It is remarkable, then, that on the very same day, April 18, Mr Hockey was also recorded as taking a $190 hire care ride in Sydney from his Hunters Hill home to Channel Seven and back again. Former federal treasurer Joe Hockey. Credit:Bloomberg The trip was recorded on a hand-written Cabcharge docket and signed by the driver on Mr Hockey's behalf. Adding to the mystery, the account details on the docket were those of a cancelled card, according to the federal department of finance. It is one of dozens of Cabcharge dockets linked to Mr Hockey's account that Fairfax Media this week revealed to have been the subject of subsequent inquiries by the department and a Cabcharge investigation in 2011 and 2012.

And it is far from the only standout example of questionable hire car rides linked to Mr Hockey's account as far back as 2009, at a cost of more than $10,000. Russell Howarth owned Ecotaxi, a car hire company. Credit:Steven Siewert Another is the $1000-plus charge racked up on Mr Hockey's account on a single day in August 2011. Driving "as directed" to Springwood, Windsor and return at the rate of $95 per hour resulted in an initial $760 bill against Mr Hockey's account for Thursday, August 11, according to one Cabcharge docket. While there are no times written on the docket, it equates to eight hours' worth of car hire.

The same day, according to separate docket, Mr Hockey was driven from his North Sydney electorate office to The Clock Hotel at Surry Hills at a cost of $58 (according to reports, he was attending a "politics in the pub" event). The return trip from Surry Hills to Mr Hockey's "residence" – presumably in Hunters Hill – is billed at $190. Finally, on the same day, there is a $110 trip from the "CBD" to a destination that is indistinguishable on the docket but looks like "local MPs". Total hire car charge for the day: $1118, roughly the cost of a flight from Sydney to London. Notably, none of the dockets are properly filled out in line with the rules for MPs using chauffeured hire cars, which require them to personally sign off on each trip and include time and destination details.

What is the explanation for these anomalies, which Cabcharge in a letter to Hockey on April 17, 2012 regarded as an "apparent fraud" involving "phantom journeys" so serious it warranted potential referral to the federal police? It's a question that is proving difficult to answer properly, even now the investigations and their subject matter are in the public arena. Mr Hockey, now Australia's ambassador in Washington, told Fairfax Media this week he had no knowledge of what was going on. Yet according to Russell Howarth, the owner of the car hire company in question, Ecotaxi, Hockey's Cabcharge details were kept on file by his firm by arrangement with his office. After each trip they were hand-written onto blank Cabcharge dockets and Hockey's signature was signed on his behalf by drivers.

"To be honest, when you've got the shadow Treasurer, who was very high-profile at the time, I kind of see that as commensurate to a business leader," Howarth explained in an interview with Fairfax Media. "Let's say we're dropping him off at a building where it says no stopping. What do you do? Do you stop the car and say, excuse me Mr Hockey, wait the 90 seconds while you electronically process it, or manually roll it? "We had a copy of his card on file and we would just write the details in. We actually did offer to invoice them and not charge them on Cabcharge. But politicians have to use Cabcharge." Compare this with Mr Hockey's explanation to finance: "There are many occasions when I do not carry my Cabcharge card on my person," he said. "There are also some occasions where equipment failure and my hectic schedule prevent the normal issue/authorisation of travel dockets".

This week he said he favoured hire cars and taxis over Comcar as it "ensured consistent and knowledgeable drivers. Unlike Comcar, taxis and hire cars are able to use bus lanes in peak hour traffic, which further saves time and money for taxpayers." Mr Howarth's explanation seems at odds with his statutory declaration presented to the finance department's entitlements management branch by Mr Hockey's office on April 27, 2012, shortly after Cabcharge's letter flagging a referral to police. In it, he declares Mr Hockey was "not aware of the invoicing arrangements" and even acknowledges that he had "been advised by Mr Hockey's office on previous occasions for the necessity to submit invoices in the manner as required". In response to queries by the finance department, Mr Hockey reassured them that the dockets submitted by Mr Howarth were for valid trips, within his entitlements, allowing Mr Howarth to invoice finance for $6700 in two tranches. Mr Howarth this week declined to tell Fairfax Media how the statutory declaration had come about, or offer an explanation for the mysterious April 18, 2011 trip to Channel 7 while Mr Hockey was in Dubai.

The Australian Federal Police referral flagged by Cabcharge in its letter to Mr Hockey was never made. In the letter, Mr Hockey was invited to personally discuss the matter with then Cabcharge chief Reg Kermode, who died in 2014. Mr Kermode's mobile number is handwritten on the letter obtained from the department of finance files under freedom of information laws. Yet Mr Hockey says he has "no recollection" of speaking to Mr Kermode or Cabcharge following the letter, as this would have been "inappropriate". Cabcharge declined to comment on whether he did. The author of the letter, Andrew Skelton, then company secretary, now Cabcharge CEO, will only say the matter was not referred to the police.

This is because it was "resolved" with the department of finance and to the satisfaction of the parties involved. However, the Australian public remains in the dark about precisely how this was resolved. As has been noted, the sum involved potentially dwarfs the more notorious Cabcharge scandal involving former federal speaker Peter Slipper, which was public at the time of the investigation into Mr Hockey's account. 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 after an investigation by the Australian Federal Police. The convictions were overturned on appeal.

This has led Greens Senator Lee Rhiannon to call for the AFP to launch a similar investigation into the Hockey revelations. Numerous questions remain unanswered, largely because the finance department's response that it "does not comment on its dealings with individual parliamentarians or in relation to the administration of parliamentary entitlements".