Third term beckons for New Zealand government as polls open

New Zealand's ruling centre-right government of John Key looks poised to be returned for a third term as voting opened in the national election on Saturday.

Opinion polls point to Key's National Party, which has been in power since 2008, being the biggest single party with about 46 percent support, with the main centre-left Labour Party trailing a distant second on 25 percent.

However, under New Zealand's proportional voting system National is unlikely to gain an outright majority and will need to renew its coalition deal with several minor parties to gain a majority in the 120-seat parliament.

The 53-year-old former foreign exchange dealer stood on his government's record of economic management and strict controls on spending, which have seen the country move out of recession and the global financial crisis to be one of the best performing developed economies over the past year.

The campaign was overshadowed by allegations of dirty political tactics involving government ministers, and claims that a government spy agency planned mass secret domestic surveillance last year, although the fallout had little impact on Key's ratings.