Leading ‘no’ campaigner Warren Mundine confirmed he had “kicked people off” the campaign because of racist comments.

Mr Mundine declined to name them, but said two people had been removed from the campaign because he heard them say something racist.

“They’re not prominent people, they were people who were working for us as volunteers,” he told ABC Radio on Tuesday.

“I’ve gotten rid of them and I don’t accept any racial comments from anyone in regard to these issues.”

Mr Mundine said the remarks weren’t about Indigenous people, but one was a “very anti-Semitic comment”.

“We have these people, they’re a minority, a tiny minority within the Australian make-up and we’re going to make sure that’s going to remain that,” he said.

But the Liberals for Yes group said Mr Mundine had raised more questions than he had provided answers.

In a statement, the group called on the ‘no’ campaign to immediately release all details about the sackings.

“This referendum debate is too important, and the eradication of racism too essential, for political cover-ups and secret sackings to be allowed to remain in the cover of darkness,” the statement said.

Support for the voice is continuing to slip, as polls show a mirroring decline in voter sentiment about the prime minister.

A referendum to enshrine an Indigenous voice in the constitution is expected to be held in October.

A Resolve Political Monitor poll conducted for the Sydney Morning Herald found support for the voice had declined from 48 to 46 per cent, on the ‘yes’ or ‘no’ question.

This means support is down from 63 per cent one year ago.

Poll results indicated the voice had majority support in Victoria and Tasmania, but not in NSW, Queensland, Western Australia or South Australia.

This suggested the referendum would not succeed because it would not reach the required double majority threshold.

To succeed, the ‘yes’ campaign will require more than 50 per cent of the vote across the nation and in four of the six states.

While Labor supports the voice being enshrined in the constitution, Liberal and National MPs at federal and state levels are split between a federally constituted federal voice, legislated local and regional voices, or nothing at all.

If added to the constitution, the voice could be modified by the parliament of the day but not abolished.

Opposition Leader Peter Dutton said the prime minister was “way off the pace” in terms of the public view on the voice.

“I understand the scepticism that’s out there,” he told Nine.

“Everybody wants a better outcome for Indigenous Australians, but I think people are really worried about a new layer of bureaucracy and whether it would give the practical outcomes in Indigenous communities that we all really want.”