Labour leader Andrew Little is hinting at downsizing a planned $20b Defence Force upgrade if he becomes Prime Minister after the election.

He says the money would be better spent on housing and education for the most vulnerable New Zealanders instead of buying new planes and ships for the military.

The 10-year $20b upgrade was unveiled last year, with plans to replace ageing planes, ships, and other defence infrastructure that had come to the end of its life.

"When it comes down to a choice between doing stuff that's going to give people a chance to get a roof over their heads or get the kids set up for opportunities for the future, that's got to come first, that is our priority," says Mr Little.

He says he will look at the $20b proposal, but says his priority is clear.