A bill imposing significant limits on MPs’ constitutional rights may have a chilling effect on MPs’ freedom of speech inside and outside Parliament, the New Zealand Law Society says.

In a submission on the Electoral (Integrity) Amendment Bill presented to Parliament’s Justice Committee, the Law Society said more evidence is needed that the limits are demonstrably justified in a free and democratic society.

Law Society spokesperson Jonathan Orpin-Dowell said the Law Society agreed with the Attorney-General that MPs’ freedom of expression would be significantly impaired by the bill.

“The bill empowers political party leaders to cause MPs to vacate their seats, and amends New Zealand’s constitutional provisions by changing the circumstances in which MPs can be removed”, Mr Orpin-Dowell said.

“MPs’ rights of free speech – described by the Attorney-General as having ‘special constitutional value’ – and freedom of association would be significantly limited, and the select committee has not been provided with sufficient evidence and analysis to justify this.”

The Law Society pointed to some cases since the introduction of MMP that would have triggered the bill’s provisions, and recommended further analysis of these.

“One rationale for the bill is that it will enhance the maintenance of the proportionality of political party representation in Parliament. The recent cases should be closely analysed to shed light on the extent to which MPs leaving their party but remaining in Parliament distorts proportionality,” he said.

If the bill is enacted, it will introduce changes to New Zealand’s constitutional arrangements that should not come into force until the next parliamentary term, the Law Society says.

“The rule of law requires that constitutional changes are made in a forward-looking way, not retrospectively, and Parliament applies this principle in relation to its own Standing Orders which are another part of the constitution,” Mr Orpin-Dowell noted.

If the bill proceeds, the Law Society has also recommended changes to clarify whether MPs have the protection of recourse to the courts.