Police Minister Mark Mitchell has accused prominent community leaders of attacking his character after they rallied behind Labour candidate Rakesh Naidoo and criticised the way Naidoo had been treated by police leadership and politicians.

Two former Race Relations Commissioners and more than 20 community leaders last week publicly backed Naidoo, expressing "deep concern" that his character had been "questioned so publicly" before any review into his conduct had been completed.

A third Race Relations Commissioner also accused Mitchell and Police Commissioner Richard Chambers of "riding tandem" in their criticism of Naidoo.

Naidoo, ranked at number 13 on Labour's list, is on leave from his role as an ethnic, iwi and communities relationships manager for police.

Both Mitchell and Chambers have expressed disappointment that Naidoo had not given earlier notice of his intention to run for the Labour Party. Chambers said he would launch an investigation into whether any sensitive information was improperly shared.

Speaking on Thursday, Mitchell rejected a suggestion he and Chambers had in any way teamed up against the Labour candidate.

"I completely, totally reject that," he said. "I would take that [suggestion] as an attack on our character."

Mitchell said both he and Chambers had "every right" to comment on matters of political neutrality within the police.

He said he felt "very strongly" that Naidoo should have notified the commissioner as soon as he entered into talks with Labour about becoming an MP, allowing police to put safeguards in place.

"The commissioner was denied that opportunity because he was informed 72 hours out, and I think anyone, any right thinking person, would look at that and think that that was not the right thing to do."

Former race relations commissioner Joris de Bres came out in support of Naidoo in a social media post on 9 June, saying the police had "no justification" for investigating whether Naidoo had shared confidential information.

"He would not do that and they know it," de Bres wrote. "He is a person of the highest ethical standards."

In a separate interview with the Herald, De Bres said: "It seems like the minister and the commissioner have been riding tandem in terms of criticising Rakesh, and I deplore that."

In an open letter published last Friday, former race relations commissioners Gregory Fortuin and Dame Susan Devoy, among others, also expressed "deep concern" at seeing "Rakesh's character questioned so publicly before any review has been completed".

"While we come from different communities, we are united in our experience of Rakesh as a person of integrity, professionalism, fairness and compassion," the letter said.

"We know Rakesh as a person of strong moral character and mana, who has consistently treated others with fairness, dignity and respect."

The letter was signed by 23 people, including former NZ Olympics trustee Dai Gilbertson, Tā Kim Workman, a justice advocate at Ngāti Kahungunu ki Wairarapa and Dave Moskovitz from Wellington Abrahamic Council of Jews, Christians, and Muslims.

Aotearoa Resettled Community Coalition chief executive officer Abann K. A Yor, former Action Station director Marianne Elliott and Ethnic Research Aotearoa chairperson Tayo Agunlejika were also among signatories.

"We have known and worked with Rakesh Naidoo over many years through our shared commitment to human rights, race relations, community wellbeing and public service," the letter said.

"Many of us have worked alongside him in challenging situations and have witnessed first-hand his commitment to serving all New Zealanders and strengthening relationships across communities."

The signatories of the letter said they were making no comment on the outcome of the review itself.

"Instead, we believe in the principles of fairness, natural justice and due process. These principles require that allegations be examined and conclusions not be reached before a fair process has run its course.

"Rakesh has spent much of his professional life advocating for human rights, social cohesion and respectful engagement between communities.

"As someone who has fought for all New Zealanders to be given a fair go - regardless of their ethnicity, religion or gender - it is especially important that those same principles be extended to Rakesh."

(This story was first published on rnz.co.nz)