The Green Party says it is having to swallow a dead rat by voting for the waka-jumping legislation.

Photo: VNP / Phil Smith

This legislation is part of the coalition agreement between Labour and New Zealand First and would prevent MPs switching parties during the term, or striking out as an independent if they are ejected from their caucus.

Similar laws have been passed by Parliament with sunset clauses, and every time the Green Party has railed against them.

In 1999, the-then Green Party co-leader Rod Donald called the legislation anti-democratic, draconian and warned it would turn MPs into robots

The Greens supported the current bill to select committee, then said they would consider whether to support it further - which they have now opted to do.

Former MPs and party members are not happy with the current caucus' decision to support the proposed law, saying it is a serious departure from Green Party principles.

Green Party MP Eugenie Sage said the party was having to swallow a dead rat.

"It's legislation I don't like, but when you are part of a coalition there are just some things you have to do as part of the coalition agreement."

However, the Green Party is not part of the coalition, and nor is it outlined in their agreement with Labour that they must support the proposed law.

When this was put to her she conceded that was correct, but said it was important to another coalition party and the stability of the government.