Nauru is sliding towards authoritarianism and New Zealand needs to take action, the New Zealand Law Society says.

Photo: Twitter/ @Republic_Nauru

Its convenor Austin Forbes QC said the rule of law on Nauru was under threat.

Of particular concern was the Administration of Justice Act 2018 which redefined contempt of court as including anything that scandalised a judge, a court or the justice system in any manner whatsoever, Mr Forbes said.

The Act makes it a crime to criticise any party in a legal case and also inhibits mainstream and social media coverage and comment on legal cases.

This measure and other recent changes raised major concerns, Mr Forbes said.

"A country like New Zealand should seek to try and influence the government in Nauru not to pass laws like this recent law relating to contempt, and to allow those who are being charged to have reasonable access to legal representation at a level that is appropriate to the charges that are being laid," he said.