WELLINGTON, Aug 28 - Ardern backs the idea of making te reo Maori compulsory, but is cautious around the education system's capacity to make it happen.

National leader Bill English announced plans at the party's campaign launch on Sunday for a $379 million education package, which includes giving every primary school student the opportunity to learn a second language.

The package also includes upskilling teachers to improve the math skills of primary school teachers, and using digital resources.

Asked how the programme could be implemented given nationwide teachers shortages, English on Monday rejected that was the case calling teacher shortages a seasonal issue.

"There isn't really a bad teacher shortage. At this time of year with the winter effects it's always a bit of pressure on schools," he told TVNZ.

He backs the idea of expanding online networked learning, where one teacher teaches in six or seven schoolsthrough digital services.

He also suggested language teachers who have gone on to different roles would welcome the opportunity to go back to a school environment.

Ardern said later on Monday while she's positive about children learning a second language she's concerned about implementation, and says the same about making te reo Maori compulsory.

"We know that the issue of lifting the number of teachers who are available for language is something we've got a big issue, a big gap [with] in New Zealand," she said.

"But it's something that we ourselves have been looking at, we'll have a little more to say on that soon."