The Morrison government wants to force local councils across the country to hold citizenship ceremonies on Australia Day, in a move aimed at locking in January 26 as the national day.

The government ramped up pressure on councils after a handful - including the City of Darebin and Yarra City Council in Melbourne - shifted ceremonies from January 26 out of respect for Indigenous Australians.

But Barry Calvert, mayor of Hawkesbury City Council on Sydney's northern outskirts, said there was no motive to move theirs, other than to escape the heat.

"We didn't move the ceremony for political reasons," he said. "We weren't dodging Australia Day.

"Last year, we had it in the marquee and it was 44 degrees, people couldn't cope, we had people leaving."

The council's staff had recommended this year's ceremony take place the evening of January 25 to avoid the heat.

"Mr Prime Minister [Scott Morrison] wants to make a determination that it should be on Australia Day so we'll find a way of doing that. I think he can stand up and say that, if that's what he wants," Cr Calvert said.

"We'll have to find some money to do that, that will be the main problem."

Australian Local Government Association president David O’Loughlin called on the federal government to help meet the costs of holding the ceremonies on Australia Day.

"There are significant additional event and staff costs associated with holding citizenship ceremonies on a public holiday, which is why some councils sensibly choose to hold it on a weekday instead."

Local Government NSW president Linda Scott, who is also deputy mayor of the City of Sydney, said local councils should have the right to choose when citizenship ceremonies were held.

"There are 128 NSW councils who will already overwhelmingly hold citizenship ceremonies on Australia Day this year, negating the necessity for the government to make it mandatory.

"A small number of NSW councils have chosen not to hold citizenship ceremonies on Australia Day because of the heat, because they don't have new citizens to swear in, or for cultural reasons."

The government also signalled the planned reforms would include a strict dress code for Australia Day citizenship ceremonies that would ban thongs and board shorts.

Ms Scott said: "It was surprising to see an Australian prime minister announcing a ban on board shorts for any event on Australia Day, and it is unclear how council staff would enforce this."

The mayor of Sydney's Inner West Council, Darcy Byrne, said residents wore "very stylish dress" to its citizenship ceremonies. The council would not enforce a dress code "from someone who can't even put his baseball cap on straight," he said, referring to Mr Morrison.

The inner city council last year hotly debated whether to ditch its Australia Day celebrations, with councillors eventually deciding to maintain the status quo.

Cr Byrne said the council would instead review its activities on that day with an aim to make them "sober and respectful" for Aboriginal people.

"The nature of that day has to change." He said the decision of when to hold the ceremonies "should be the remit of local councils, obviously".

"I think it would be a disaster to play into [the federal government's] hands to cancel the citizenship ceremony and then lose the power to hold citizenship ceremonies at all."

Byron Shire Council last year backflipped on its decision to shift all Australia Day events from January 26 out of respect to Aboriginal and Torres Strait Islanders, after the Morrison government in turn stripped the council of its right to hold citizenship ceremonies.

Kempsey Shire Council also previously defended its decision to hold its citizenship ceremony on January 25.

The council on the Mid North Coast said in November its ceremony had been held alongside its Australia Day awards event on the 25th, in line with the national awards ceremony in Canberra, for four years.

In Melbourne, the federal government banned Darebin and Yarra councils from having citizenship ceremonies after they refused to hold the events on Australia Day.

Yarra Mayor Danae Bosler said January 26 was a day of mourning for indigenous people and not an appropriate time for a national celebration.

“We have a strong and longstanding relationship with our local Aboriginal community, and we’re very proud to stand together with them on this important issue."

In an opinion piece for The Age, Darebin mayor Susan Rennie wrote that forcing councils to hold citizenship ceremonies on January 26 was “at worst a public relations stunt designed to further divide this country and stir the dying embers of a culture war”.

A third council, Moreland, will also show its opposition by holding a citizenship ceremony on January 26 without making references to Australia Day.

“We try and refer to the day as January 26 because it is neutral,” deputy mayor Mark Riley said.

Councils will have an opportunity to provide feedback on the proposed changes.