Tony Abbott probably knows where his first dollar came from. His preoccupation with how much money is coming through the door is legend in Canberra amongst his colleagues.

Indeed the first thing to come out of Abbott's mouth at the outset of the leaders' debate concerned his personal finances. "This election is about a fair go for families struggling with the cost of living pressures," Abbott declared. "My wife Margie and I know what it's like to raise a family, to wrestle with a big mortgage, with grocery bills and school fees."

Immediately after John Howard's 2007 election loss Abbott dubbed the period a "grieving" phase. But Abbott was lamenting more than just the fact that the Liberals had ceded power to Kevin Rudd. He mused publicly on the shock of losing his ministerial salary, complaining he didn't know how he was going to pay the bills.

Bills of the type that might be incurred in a national book tour for example. Department of finance documents raise the serious and politically damaging possibility that Abbott used taxpayer money to promote his 2009 book, Battlelines.

The revelation follows an investigation by The Drum in which the dates of Abbott's national book promotion tour have been matched to his travel expenses claims. The dates of his promotional tour were provided by his publisher, Melbourne University Press.

Abbott's home base is Sydney where Sarah Murdoch launched Battlelines on Tuesday, July 28. Two days later, the then-Opposition frontbencher flew to Canberra, to quote MUP, "address the National Press Club (NPC) to discuss Battlelines". There was also a book signing coinciding with the event.

According to the department of finance report detailing entitlements paid to MPs and senators from July 1 to December 31 2009 and tabled in the Parliament on the eve of the election, on July 30, the day of the NPC address, Abbott billed taxpayers $504.29 for the round trip flight back to Sydney.

On August 3 Abbott was in Melbourne for a Dymocks bookstore "Dinner Event" held at George's Restaurant in Camberwell. Abbott billed the return flight to Melbourne on the same date to taxpayers. Cost: $930.95.

On August 6 Abbott was in Melbourne again for a "Liberal Party Book Club Event". Again he booked the cost to the taxpayer, flying back to Sydney the next day; $465.47 each way. Then it was on to Brisbane on August 11 to promote Battlelines in an appearance at the Brisbane Institute. Total cost of the round trip, including a stopover in Canberra on August 12; $861.95.

Then came Perth on August 14 and 15. This time it was an event co-sponsored by The West Australian newspaper and Dymocks. According to the department of finance figures the total round trip cost was $2,461.23.

The total for all Abbott's travel that coincided with promotional events for the book comes to $5,689.36. That's a sizeable chunk of Abbott's total air travel costs of $29,633.85 for the same period. Then of course there's the cost of the Commonwealth cars and drivers that he also billed to taxpayers on the days he was promoting Battlelines. That final tally: $962.60.

All in all the taxpayer coughed up $6,651.96 in Battlelines-related travel.

At the very least these expenses are politically awkward. Was he also doing government business in the places where he promoted his book? Even if he was, is it appropriate to plug your book while you're there when taxpayers are paying the travel bill? Remember the savage gusto with which the Opposition, Abbott included, went after Kevin Rudd and former defence minister Joel Fitzgibbon over claims they had not properly declared privately sponsored air fares to China.

A spokesman for Tony Abbott dismissed the allegations as a smear campaign.

"All travel undertaken by Mr Abbott has been within the entitlement. This is a blatant attempt by Labor to smear and mislead."

But this time, Tony, it's your turn to provide some answers.

Glenn Milne has been covering Canberra politics for more than two decades. He was a delegate to the current American Australian Leadership Dialogue.

How the taxpayer helped Tony Abbott flog Battlelines