The latest expense returns for MPs reveal thousands of dollars spent on political campaigning, a four-figure taxi fare and birthday presents for an 11-year-old girl.
Records released by the Department of Internal Affairs showed MPs and ministers spent $2.4 million on travel, accommodation and other expenses in the past three months - slightly less than for the same period last year.
During this time several ministers travelled to the Northland electorate to campaign alongside National candidate Mark Osborne. While ordinary MPs were not permitted to use taxpayer-funded cars or accommodation for campaigning, ministers could use Crown limos "at any time for any purpose, at the minister's discretion".
The records showed Transport Minister Simon Bridges spent $10,455 in the past three months, of which $6519 went on flights and Crown limos in Northland.
Speaking about his Northland trips, Mr Bridges defended the spending: "Clearly ... some of what I did was party political but I also did a significant amount of Crown business and I think that was important work.
"I think ultimately ministers of the Crown have to operate like ministers of the Crown and that involves significant travel throughout New Zealand and that's the case whether it's a byelection or not."
Steven Joyce, who ran National's Northland campaign, had total ministerial expenses of $14,481 - $4000 more than last year - though it is not yet known whether any of this total was spent in Northland.
The returns showed Mr Joyce also racked up a taxi fare of $1248 during a visit to Australia in November after keeping the meter running for nine hours.
A spokeswoman said Mr Joyce had a full day of engagements while in Sydney for a job fair and he saved money by making a day trip to Australia and not staying in a hotel.
His office pointed out that if he had used a Crown limo for the same length of time it would have cost a similar amount.
While Labour was critical of National's spending in Northland, its leader, Andrew Little, also had relatively large travel and accommodation bills in the past three months.
Mr Little, who is based in Wellington, spent $25,816 on domestic travel. That was more than his Auckland-based predecessors David Cunliffe and David Shearer spent over a similar period. Mr Little's office said he visited Northland three times during the byelection. And, as a new leader, he made a number of regional visits to meet constituents.
Presenting a New Zealand touch
What to get the 11-year-old daughter of a millionaire Prime Minister?
Ministerial credit card records show Prime Minister John Key chose distinctly New Zealand gifts for Nancy Cameron - daughter of British Prime Minister David Cameron - when he crashed her 11th birthday lunch in January.
Mr Key and wife Bronagh gave Nancy the Joy Cowley book Dunger, pineapple lumps, Jaffas, Whittakers chocolate, an SPCA cat calendar and a copy of Lorde CD Pure Heroine.
The Keys attended the occasion ahead of talks between the two leaders.
Mr Cameron was given New Zealand wine and his wife, Samantha, received a $220 possum-fur scarf.
Fearing the other siblings would be neglected, Mr Key also bought Arthur and Florence Cameron lollies, rugby socks, a torch, a beret, a puzzle and books.