WELLINGTON, March 22 (Xinhua) -- The New Zealand government announced Wednesday it is opening up almost half a million square kilometers to oil and gas prospecting this year.

The 2017 block offer was announced as climate change protestors disrupted New Zealand's annual Petroleum Conference in the energy hub of New Plymouth, on the west of the North Island, temporarily shutting down the industry gathering.

Energy and Resources Minister Judith Collins, who made the announcement at the conference, was also criticized by opposition lawmakers who said the more than a third of a sanctuary for the world's rarest dolphin was included in the prospecting area.

In a published speech, Collins acknowledged the last few years had been particularly challenging for the industry as global markets experienced an oversupply of oil and low prices.

"This has created an extremely tough operating environment for all in the sector, and New Zealand hasn't been immune," she said.

"The global exploration and production industry is cyclical the low number of permits granted in last year's Block Offer reflects a significant downturn in the sector," Collins said.

"However, activity in New Zealand and globally is expected to pick up as operator margins improve."

This year's block offer included five offshore areas, two onshore areas and one offshore-onshore area, comprising 5,102 square km onshore and 476,632 square km offshore.

"New Zealand's petroleum sector is small by global standards but is nonetheless a significant contributor to the economy. Between 2011 and 2015, oil companies invested 7.7 billion NZ dollars (5.41 billion U.S. dollars) in oil and gas exploration and production in New Zealand," she said.

The opposition Green Party said the government had opened up 35.5 percent of the North Island Maui's dolphin sanctuary for drilling, as well as scenic coastal areas, creating major risks for New Zealand's "clean and green" tourism brand.

"There are only 63 Maui's dolphins alive and drilling for oil and gas in the area that's supposed to be their sanctuary puts every one of them at risk," Green Party energy and resources spokesperson Gareth Hughes said in a statement.

"This is the largest amount of the Maui's dolphin sanctuary ever opened up for oil and gas exploration, ironically at a time when oil companies are giving up on exploring in New Zealand," he said.

On Tuesday, Collins had revealed the government faced liabilities of up to 855 million NZ dollars (601.06 million U.S. dollars) for decommissioning old oil rigs and the next day it was opening up new areas for oil exploration and drilling, said Hughes.