Winston Peters has outed Labour today, accusing it of trying to use a sledgehammer to smash a nut with its rent relief for small businesses.

The New Zealand First leader says his coalition partner wanted to alter contract law for all lease arrangements.

He says that would have been poorly targeted.

Peters has been accused of holding up the rent relief for small businesses announced today.  

But he's come out fists flailing, saying the Government needs to show they're aware of the fiscal costs of every decision.

He says that's why he's insisted on the better targeting in today's changes.

Prime Minister Jacinda Ardern by saying that's how politics works.

"It's election year so parties will push their agendas, but what matters is building consensus, and that's what we've done with small businesses."