National believes there's another reason for Minister Nanaia Mahuta to be sacked.

It's been revealed the minister was advised against the controversial Three Waters entrenchment clause on October 25th - a month before she took it to caucus.

National's Chris Bishop says caucus decided against the clause in May.

He told Tim Dower the Prime Minister needs to show some leadership and sack Mahuta.

A spokesperson for Mahuta says officials weren't working on entrenchment policy in October, and instead were providing advice on a wide range of changes requested by Green MP Eugenie Sage.

LISTEN ABOVE

• Revealed: Mahuta received officials' advice a month before 3 Waters entrenchment vote
• John MacDonald: Three Waters is still a dog's breakfast