Prime Minister Jacinda Ardern told a business audience in Wellington that gas was used as a "crutch" which slowed the move to renewable energy, three people who attended say.

As the industry prepares to meet for the annual New Zealand Petroleum Conference in Wellington, the future of exploration has come into question.

On March 19 Ardern personally accepted a petition from Greenpeace calling for an end to exploration, where she said the Government was "actively considering" the issue.

CAMERON BURNELL/STUFF Anti-deep sea oil drilling protesters in Wellington in 2014. Protesters have vowed to blockade the annual New Zealand Petroleum Conference in Wellington.

Two days later she spoke at a breakfast which was part of a series of events run by Wellington employment lawyer Peter Cullen.

READ MORE: Government 'actively considering' call to end oil exploration

The events have been running for several years, run under Chatham House rules, which are meant to prevent those in attendance from disclosing what they were told at the event.

ROSA WOODS/STUFF Prime Minister Jacinda Ardern during her weekly post-Cabinet press conference on March 19.

During a question and answer session, a school pupil at the event raised the issue of oil exploration, at which point Cullen is said to have invited a comment by Chris McKeown, a senior employee at New Zealand Oil & Gas.

Ardern is said by people who attended the event that she was aware that gas can be a "crutch" to inhibit the transition to renewable energy generation. She also noted that the highly cyclical nature of the industry had an impact on regional economies.

The prime minister declined to comment beyond a short statement.

"It's an inaccurate representation of what I said and given it's Chatham House rules I cannot comment any further."

All three of those who spoke about the comments were given the impression that the comments were broadly anti-gas and appeared to show she did not believe claims from the industry about the need to secure more gas to smooth the transition to renewable energy sources.

On Tuesday morning, Energy Minister Megan Woods will address the petroleum conference, which is being held at the TSB Arena in Wellington. Woods' office has indicated she will speak to the protesters.

Oil Free Wellington has called for support to "non-violently blockade" the event, claiming similar action disrupted the 2017 event for several hours.

Cameron Madgwick, chief executive of oil and gas lobby group Pepanz, urged protesters to "obey the law and respect other people's rights as well".

"People have the right to go about their daily business and attend events like this."