The National Party amassed donations worth nearly $180,000 to help Sam Uffindell win the Tauranga seat in June's byelection.
The donations dwarfed that received by rival candidates, including that of the second-highest polling candidate Labour list MP Jan Tinetti, who did not declare any party funding.
In total, Tauranga byelection candidates received $251,018.98 in donations.
Uffindell declared $176,568.98 in donations from the National Party for his campaign to replace former Tauranga MP Simon Bridges.
An Electoral Commission breakdown of byelection candidates' donations and expenses during the campaign period revealed the total was donated "in kind" to Uffindell's cause.
Donations declared can be for money, goods or services considered to be worth reasonable value. Under the Electoral Act, candidates are required to report their donations and expenses after a parliamentary election. There is a range of offences under the act for failure to comply.
In addition to the $176,568.98 from the National Party, another $2500 came from Tauranga resident M O'Reilly.
Uffindell declared $39,483.53 in campaign expenses.
Uffindell said he was appreciative of the donations which he acknowledged as being "a lot".
"I didn't go around asking for them, that was done by other people but what I think it highlights is how much the support has shifted and how strong of a desire there is in the community to see change," he said.
"I think it reflects the strength of the National Party and Christopher Luxon, and how strong National is in Tauranga."
But just weeks after securing the byelection win, Uffindell was embroiled in controversy when details emerged that as a student, Uffindell had been asked to leave King's College after a violent attack on a younger boy.
Uffindell admitted he had been a bully during his time at the school, and was stood down from Parliament amid allegations of further bullying behaviour at university. He was later reinstated to caucus after a report by Maria Dew KC found the university claims could not be substantiated.
Uffindell acknowledged he needed to "repair the faith" his donors had invested in him and "redeem myself" to Tauranga voters.
"I'm going to work extremely hard to make sure the people of Tauranga want to reelect me and work extremely hard to be a part of a team.
"… I've got a lot of work to do."
A National Party spokesman said the "in-kind support" from the party to Uffindell was in line with the 2018 Northcote byelection where almost $150,000 in donations were declared from the party to the candidate's campaign.
"The National Party's operations are funded by the generous support of our members and supporters across the country," the spokesman said.
"Tauranga is extremely important to National and to New Zealand. It is a seat we wanted to win and one we will continue to fight hard for to be able to represent the people of Tauranga."
Uffindell's National donations included goods and services, meaning there was no physical money left over.
In total, Tauranga byelection candidates received $251,018.98 in donations.
Tinetti received $9000 but spent $22,358.12 - more than half ($14,013.95) of this was on digital marketing.
"Most of our donations came in small amounts from New Zealanders from all walks of life and [this was] one of the reasons I worked with Labour to make sure that it's all audited to make sure it's above board," she said.
Tinetti did not receive party funds for the campaign but said she had "excellent support" regardless.
"It's just the way Labour does it - it does the same with the general election. If you look at all of the smaller donations and any bigger donations, you will see they are Labour Party people like Labour-affiliated unions."
The donations were made by Tauranga residents Heidi Tidmarsh and Sandy Scarrow, the Rail and Maritime Union, and the Maritime Union of New Zealand.
"The members of the party, that's really important, we are a grassroots party, a lot of the smaller donations that came in were from party people."
Tinetti also said her campaign was very much "run locally" as opposed to coming from Wellington headquarters.
Act Party's Cameron Luxton, the third-highest polling candidate, declared the highest expenses of the campaign at $48,420. Most of this ($30,909.26) was spent on digital marketing.
Luxton also declared recieving $2000 from Tauranga resident John McGrath in donations.
"The campaign was all about making sure that [the] people of Tauranga had a choice. To get that message out there, we had to invest in advertising and signage," he said.
"It was worth it to give the people of Tauranga a real choice. Hopefully, the investment will pay off in the future."
Luxton said the Act Party helped logistically and financially but the party was not listed in his declaration of donations.
An Act Party spokesperson said the election expenses were paid for by the party and donations received purely for Luxton were declared.
New Nation Party candidate Andrew Hollis, who polled fifth, declared the second-highest amount of donations with $55,400. He declared $44,480.74 in campaign expenses.
Hollis' donations came from Michael and Trena Jacomb, who donated $26,800 and $28,600 respectively.
New Zealand Outdoors and Freedom Party candidate Sue Grey, who polled fourth highest, was given $4750 in donations from Aucklander Will Watson and declared $36,315.77 in expenses.
Unlike all other candidates, whose expenses all related to various forms of advertising or marketing, Grey's also included $1230.04 for fuel and $268 for hall hire.
Independent candidate Gordon Dickson declared an $800 donation from Mainland Partners in relation to a Toyota Hilux supplied during the campaign.
In his $525 expenses bill, Dickson declared his nomination fee, fuels and tolls, stationery and phone calls.
No other candidates received donations but some declared expenses.
New Conservative candidate Helen Houghton declared $3560.22 for campaign advertising, as did One Party candidate Allan Cawood who spent $5959.46 which included $12.98 for thank you cards.
Aotearoa Legalise Cannabis Party candidate Christopher Coker spent $3125.86, most of which was on digital marketing.
Independent candidate Yvette Lamare declared $300 for her electoral fee.
Candidates Tony Corbett and Peter Wakeman received zero donations and declared no expenses.
An Electoral Commission spokeswoman said that while the amount spent on election advertising during the regulated period was expected, not all campaign funding had to be reported.
"For example, money a candidate pays towards their own campaign is not a donation for the purposes of the electoral finance rules," she said.
"Regarding donations from a candidate's political party - donations from a party (or any other donor) of more than $1500 need to be declared in the candidate's return.
"Candidates do not have to report donations (on their own, or aggregated from the same person) of $1500 or less."