Forest and Bird says Antipodean albatross are declining at an alarming rate due to being caught up as bycatch by longline fishers, in both international and New Zealand waters.
It is calling for better fishing rules in a National Plan of Action for Seabirds which is currently in its draft stage, with submissions closing on 27 January.
Forest and Bird said the albatross have a nationally critical threat status.
Seabird advocate Sue Maturin said the albatross population had been declining rapidly since 2004 and the number of females had halved.
''So now we have a situation where there are more males than females, so the poor old males are sitting there waiting for a female to come back and they are losing their mates.
''We suspect they are losing most of their mates at sea in the international fishery.''
Maturin said getting information on the numbers killed at sea was difficult, but it was estimated to be in the hundreds.
''There are not that many observers on the boats and so they are not necessarily recorded and observers don't necessarily identify down to a species level.''
The Antipodean albatross are one of the world's biggest birds with a wingspan of 3m or more and can live up to 50 or 60 years old and mate for life.
''They get drowned mostly. They get caught on a longline hook and get drowned," Maturin said.
She said albatross we slow breeders.
''Their population can't bounce back easily.''
Forest and Bird want the fishing rules tightened up considerably.
''They need to be the world's best practice," Maturin said.
She said they should not discard bait, offal and fish waste into the water and certainly not when setting or hauling in lines and nets. She added that more cameras were needed on boats to monitor the situation.
''Because we just don't know what happens at sea.''
Forest and Bird believe that Antipodean albatross will become functional extinct within 20 to 30 years if something is not done. To highlight the problem, Forest and Bird has declared 2020 to be the Year of the Seabird.
''We don't have long and we really have to put these rules in place and we really have to up our compliance," Maturin said.
Seafood New Zealand chief executive Tim Pankhurst in a statement said the capture of Antipodean albatross was upsetting, given its endangered status.
However, he said research had shown that the domestic fishing industry was not the main driver of the decline in population but rather captures on the high seas - or potentially unknown environmental factors.
"Having said that, the industry continues to take proactive steps to mitigate its impact on all seabirds, including the Antipodean albatross."