"I've got some sympathy for it," National leader Simon Bridges told The AM Show on Monday.

"If you look at the executive right now, we've got 31 on it. It's the biggest, the flabbiest executive we've ever seen. You've got to say there's a bit of a sense of jobs for people who don't necessarily need them."

The current executive consists of 20 Cabinet members, eight ministers outside of Cabinet and three Parliamentary under-secretaries - a total of 31. Before being booted from office, the National-led Government had 20 Cabinet members, seven ministers outside of Cabinet and one under-secretary - Mr Seymour - for a total of 28.

Mr Bridges was less keen on reducing the overall number of MPs.

"Take some of the South Island seats - some of them are already bigger than the state of Israel, so you'd be ramping up the size of them."

Reducing the size of Parliament by 20 MPs, assuming they're all backbenchers with no ministerial responsibilities, would save the taxpayer $3.2 million in salary costs out of a total annual expenditure of nearly $80 billion.

Accused of stealing the policy from rivals New Zealand First, Mr Seymour said Winston Peters had "completely sold out" and couldn't be relied on to get it done.

"This policy is something Winston Peters said he'd make a bottom line - they guy had more bottom lines in the election than a 100-year-old elephant. Now he's the Deputy Prime Minister and he's doing nothing about it."