A bill forcing judges to disclose their pecuniary interests is being challenged because of fears it could deter potential judicial members and risk security.
Green party MP Kennedy Graham's Register of Pecuniary Interests of Judges Bill would require all judges to make an annual return to the Judicial Conduct Commissioner of their financial interests.
This would then be made public, similar to the annual register of MPs' interests.
The bill passed its first reading and is currently before select committee.
At a hearing today New Zealand Bar Association committee member Justin Smith told MPs that judges were constrained by the law and facts, where politicians were not.
"We think that the position of judges and politicians for instance is easily able to be distinguished. Unlike politicians judges … are constrained by the law, they are constrained by the evidence which they receive, they can't depart from or reinvent the law."
He outlined the reasons why the association opposed the proposed law change.
"We question whether there is a necessity for this bill at all, we've survived an awfully long time without it."
Similar proposals had been turned down in Australia and Wales, Smith said.
Judges tended to be people who had been successful in their professional lives and would therefore have accumulated pecuniary interests.
"People who are otherwise suitable for appointment to the bench are simply not going to be keen to disclose the nature of the trust interests that they hold, where their holiday bach is etcetera."
There were already some negative impacts for those who did become judges; loss of freedom, lower income than available in practices.
"It really doesn't take a lot extra for an otherwise-suitable candidate … to decide no."
Judges were already constrained by the ability of people to appeal their decisions and the judicial conduct commissioner.
"Constraints the equivalent of which are not found so far as politicians are concerned."
And there was a lack of evidence to suggest there was a decline in public concern about the judiciary, Smith said.
Dr Graham was prompted to draft the bill after Supreme Court judge Justice Bill Wilson resigned in 2010 over allegations of a conflict of interest in a case he presided over.
Labour MP Charles Chauvel said others had told the committee there was room for improvement.
"It is really enough to say 'look things are fine, public confidence is as high as it needs to be and we don't need to do anything more that might have the effect of deterring good applicants for judicial office'?"