The government is set to crack down on environmental protesters with fines of up to $100,000 or a year in jail for those who target offshore oil and gas operations.

Energy minister Simon Bridges today announced "stronger measures to protect offshore petroleum and minerals activity from unlawful interference".

Individuals who intentionally damage or interfere with mining structures, like rigs, or vessels face a 12-month prison sentence or a $50,000 fine. Organisations face a penalty of up to $100,000.

Activists who break a 500-metre "no-go" zone around structures would be liable for a $10,000 fine.

Green party MP Gareth Hughes has branded the moves the "Petrobras law" - after the Brazilian oil giant - and said the government was criminalising protests in New Zealand's exclusive economic zone (EEZ).

Bridges said cabinet hae approved changes to firm up the protection of deep sea oil and gas exploration and give police and the navy more powers.

"There have been attempts to seriously disrupt lawful mining and related activities in recent times. These types of actions can impose significant costs on companies carrying out legitimate activities under permits, and present very serious health and safety risks," he said.

The changes will be an 'effective deterrent" against "unlawful interference" with exploration and production.

But Hughes said protests at sea were an "honourable tradition".

Citing changes to employment legislation made to mollify the makers of The Hobbit movies, and controversy over the SkyCity national convention centre, Hughes believed there was a trend to change rules to benefit a "corporate few".

Labour's energy and resources spokeswoman Moana Mackey said the ban of protesting within 500m of structures and vessels was a "massive overreation".

She also said the government was "kow-towing" to foreign-owned companies.

Bridges should make public which companies lobbied for the changes and if any deal was done in exchange for investment, Mackey said.

"The Government has pushed ahead with granting permits against the wishes - and often without even informing affected communities - and have put in place incredibly weak legislation regulating the activity in the EEZ.

"Ironically it looks like there will now be tougher regulation for protestors than for prospectors in our EEZ."

The government is pushing the oil and gas industry as part of its economic growth strategy. Oil is New Zealand's fourth largest commodity export and oil and gas production contribute more than $2.5 billion to the country's GDP.

Bridges said the changes to the Crown Minerals (Permitting and Crown Land) Bill are made in a Supplementary Order Paper (SOP) to be tabled in Parliament.