The league would replace the existing under-23 and national provincial tournaments, which are held annually over four days.
There is not yet a ''concrete plan'' for the proposed league, but NNZ head of high performance Steve Lancaster said a competition review made it obvious a tier below the ANZ Championship needed to be created.
''We need to have some form of ongoing structure between post-secondary school level and the ANZ Championship,'' he said.
''When we look at what's required for teams and athletes to be successful in terms of their physical preparation, tactical appreciation, the ability to recover every week and the mental skills of playing in an ongoing competition, competing in a one-off four-day tournament once a year doesn't prepare athletes for that level of competition.''
Asked if the lack of a national league had contributed to the growing gulf between the Silver Ferns and Australia, Lancaster said he did not think there was a direct link.
However, he does believe the creation of one will create a greater depth of players capable of performing at a higher level.
''Having a competition structure that our Silver Ferns can play in [ANZ Championship], and then have a competition structure underneath that provides really good athletes in that next tier of competition - we think, if we get that right, it will absolutely support the Silver Ferns,'' he said.
The format, how many teams would play in the league, when it would run and how it would be financially viable were not yet known, Lancaster said.
''We need to progress that through a feasibility study,'' he said.
''Obviously, anything that has a national format comes with a significant cost structure. So we need to understand what the different permutations are and what the cost structures would be that are associated with those options.''
NNZ had originally hoped to have a detailed proposal ready sometime in August, but Lancaster believes that is ''maybe a bit optimistic''.
He doubted a proposal would be ready by the end of the Netball World Cup (August 16), and said September was more likely. With plenty of work to do before the proposed league becomes a reality, Lancaster could not guarantee it would launch next year.
''We would certainly like it to,'' he said.
''Going through an overall review of our competition structure, it's come through clearly that this is the greatest need. It would be disappointing if we had to wait two years before we can introduce something.''
Dunedin Netball will discuss the proposed league at a board meeting tonight, but general manager Lee-Anne Anderson said she knew little about it.
''Until they give us a proposal and we see what that means and what the impact is to our centre and zone, I guess we don't really know what change it means,'' Anderson said.
''It's been talked about for a long time. We have got ANZ Championship level but we don't have anything underneath it.''
This year's national under-23 tournament starts in Auckland on July 6, while the national championships start in Ashburton on September 28.
