MORE areas are going to be opened up for oil and gas exploration in New Zealand, Prime Minister John Key says.

He told a conference in Auckland on Monday the government wants to see a "significant expansion" in exploration by international companies, Radio New Zealand reports.

Mr Key says the industry could be a game changer for New Zealand and the government is backing plans to open up onshore and offshore exploration areas outside Taranaki.

He believes the next five years will be crucial, with extensive exploration planned which could secure New Zealand's energy future.

Mr Key was speaking to more than 500 delegates at the Advantage NZ: 2013 Petroleum Conference, hosted by the Ministry of Business, Innovation and Employment.

It opened on Monday and runs for three days.

Since it came to power in 2008 the government has had a policy of encouraging oil and gas exploration.

It wanted to allow exploration in protected conservation land but had to scrap that because of strong public opposition.