Despite thousands taking part in strike action this year, union membership continues to decrease

Unions are acknowledging the need to change to stay relevant as numbers continue to decrease.

Unions fight to remain relevant as membership drops from half a million to about 300,000. Source: 1 NEWS

Despite thousands of workers taking to the streets several times this year, only 18 per cent of employees in New Zealand are members of unions.

"It's become more accepted, certainly amongst the younger workers, that you don't have to join the union and in fact most workers realise unions will get them benefits whether they're part of the union or not," Victoria University professor Stephen Blumenfeld told 1 NEWS.

New Zealand's most violent and disruptive industrial confrontation happened in 1913 when 16,000 watersiders and miners to part in strike action.

Another waterfront strike in 1951 wasn't as violent, but was one of the longest, lasting 151 days.

In the following decades the number of strikes reached an all-time high. But the big change came in 1991 when a law change saw more employees negotiating directly with employers.

Union membership has dropped from half a million to around 300,000.

"It means there's less money in the union coffers and it costs money to be effective," said Mr Blumenfeld.

Recent long-running strike action with nurses has now been solved, but this week teachers plan to walk off the job proving unions still have a voice.

"Unions are now pushing for causes that are really salient for young workers," said Mr Blumenfeld.

"Unions are actually part of the overall movement for social change and I think a lot of young people are seeing the union as an avenue for them to be engaged in other campaigns, so things like climate change and its impact on the future of work," said PSA Union's Lauren Hourigan.