More than 50 members of the Administrative Appeals Tribunal – the independent authority that reviews decisions by the Australian government – have been told they will not have their contracts renewed, after attacks from ministers over decisions the government did not agree with.

The Guardian has been told at least 50, most from the migration and refugee division of the tribunal, have been told they will not be reappointed.

The AAT has been heavily criticised in News ​ Corp newspapers and by the immigration minister, Peter Dutton, for overturning government visa decisions in the past year. The AAT assessed 11,300 visa decisions in the year to April, overturning 39% of Dutton’s decisions.

The criticism focused on a number of particularly controversial cases – the decisions of which have not been published publicly by the AAT – including six Iranian nationals determined to be refugees who had returned to visit Iran, and Jagdeep Singh, a Melbourne taxi driver who pleaded guilty to indecently assaulting a woman.

Dutton condemned the decisions of the tribunal, implying they were motivated by ideological opposition to the government.

“When you look at some of the judgements that are made, the sentences that are handed down, it’s always interesting to go back to have a look at the appointment of the particular Labor government of the day,” he told 2GB radio.

“Anyway, it’s a frustration we live with.”

Law Council of Australia President Fiona McLeod condemned Dutton’s comments as an attack on the judiciary’s independence, saying tribunal members reviewed­ government decisions “in accordance with law, not personal preference or ideology”.

“Any suggestion by government that Australian jurists­ are not acting with independence is dangerous and erosive to our justice­ system,” she said. “It undermines the public perception of the legitimate role of the judiciary and weakens the rule of law.”

The minister holds an unchallengeable authority to overrule the decisions of the AAT in visa cases on character grounds. New sections were introduced into the migration act by former immigration minister Scott Morrison to give the minister greater powers to overrule AAT decisions.

The original power to overturn the AAT was introduced by Philip Ruddock, when he was immigration minister in 1999, again over government dissatisfaction at tribunal decisions.

In the Singh case, Dutton overturned the AAT’s decision and ordered Singh to be deported.

The AAT has 324 members, 94 of whom work full-time. Sixty-five of the 77 members whose terms are due to expire at the end of this month work in the migration and refugee division.

The term of the president of the AAT, former Labor minister Justice Duncan Kerr, expired last month. A replacement has not yet been appointed.

A spokesman for the attorney general, George Brandis, said the terms of a “large number” of tribunal members expire on 30 June.

“Appointments to the AAT are for a fixed term, usually five or seven years. The government will be announcing appointments to these vacancies in the ordinary course.”