The Green Party spent $1.5 million on its election campaign last year - more than double its 2005 amount - and says the increase was because it was erring on the side of caution as a result of the Electoral Finance Act.
In 2005, the party spent $586,000 on its campaign - just 29 per cent of its spending cap.
Election-expense returns released yesterday showed that in 2008 the Greens spent $1.46 million - two-thirds of their $2.2 million limit and outstripping even the Act Party, which was traditionally a big spender.
The Green Party increased its number of MPs by two - from seven to nine.
The other parties' spending was similar to previous years. National and Labour both came close to their election spending limits of $2.26 million and $2.4 million respectively.
Act spent $1.14 million on its campaign and got five MPs into Parliament.
The Maori Party got a better bang for its buck - spending just $222,000 for the same number of seats.
Green Party co-leader Jeanette Fitzsimons said the higher-than-normal total was partly because of the longer election period.
Under the Electoral Finance Act, the election period began on January 1 rather than three months before polling day.
She said the party also took a precautionary approach to ensure it did not accidentally fall foul of the Electoral Finance Act. Some of its declared spending was probably not required in law.
The now-repealed Electoral Finance Act left its mark - several of the auditors' reports carried qualified opinions, citing "current uncertainty" about what was considered election advertising and an inability to determine whether spending was publicly funded.
The Greens were also the only party to declare how much of their spending was funded by the taxpayer through the Parliamentary Service.
It said about $187,000 was parliamentary spending which it believed was material generated in its MPs' normal course of duties. It had stopped using such material after Parliament rose for the campaign proper.
National's $2.21 million included $349,000 for producing its television advertisements.
Labour spent slightly more than National overall on $2.26 million, which included $244,000 on television advertisements.
Labour, the Green Party, the Progressives and the Maori Party all had to include $35,000 for a Council of Trade Unions ad which supported the parties. The Electoral Finance Act required spending to be apportioned between parties in such cases.
No parties exceeded their caps, unlike 2005 when Labour got into trouble for its parliamentary-funded election year "pledge card" - a cost which was later deemed an illegal election expense and put it over its spending cap.
New Zealand First has not yet returned its election expenses and the Electoral Commission will meet next month to decide what action to take.
* Labour: $2.26 million43 seats
* National: $2.21 million58 seats
* Green Party: $1.46 million9 seats
* Act: $1.14 million5 seats
* Maori Party: $222,0005 seats
* Progressive Party: $168,0001 seat
* United Future: $152,0001 seat