"Waka-jumping" legislation gives NZ political party leaders too much power, instead of forcing them to follow the will of the electorate, says National leader Bill English.
The new bill that has been introduced to Parliament is part of the coalition deal between Labour and New Zealand First, and would stop elected MPs from jumping between parties.
Mr English told Morning Report the National Party was opposed to the bill on the principle that people were elected on the basis on the electoral law, and not the will of the party leader.
He said the new government was trying to impose an extra degree of discipline on its MPs.
"It just gives party leaders - and I'm one - too much power over who is in parliament and who is out of parliament."
Watch the full interview with Bill English here:
MPs who have left their party but stayed on in Parliament in the past include Peter Dunne, Jim Anderton, several NZ First MPs in the late 1990s and a slew of National MPs in the early 1990s
Mr English said there had been 'messy' periods of jumping, but that did not mean there was need for a new law.
"Parliament has just got to deal with it, it's dealt with it plenty of times before quite capably."
Mr English said it was legislation that only NZ First had been interested in, but he would not discuss if it was part of the negotiation process after this year's election.