Bill Shorten has confirmed Labor is open to cutting Australia's migrant intake but warned against "dog whistling" on population policy.
Prime Minister Scott Morrison has once again floated the idea of slashing the number of migrants allowed into the country each year, without announcing a proposed cap or any other new policy settings.
He has defended reviving the population debate so soon after the Christchurch terror attacks, where the Australian alleged far-right gunman is accused of harbouring hate against Muslim immigrants.
"It's always the right time to be addressing the issues and needs that the Australian public are concerned about and want addressed," Mr Morrison told reporters in Adelaide on Tuesday
"This debate about population growth and migration has nothing to do with those other issues that have been the subject of recent focus."
For many months, the government has floated plans to reduce Australia's migration ceiling by 30,000 from its current level of 190,000.
This would essentially match last year's actual intake of 162,417.
"This isn't exactly earth-shattering," Mr Shorten told reporters in Perth.
"What this bloke has done is announced this year will be the same as last year - that's fine by me."
But the Opposition Leader said there were broader lessons to learn from the Christchurch mosque massacre, which has left 50 people dead and dozens more injured.
He said right-wing extremists and "crazies" took comfort in politicians going down the "slippery path" of bagging immigration.
"The dog whistling by political leaders about immigration and asylum seekers must stop," Mr Shorten said.
"We all know that for a number of years, the slow slide into the sleazy attacks on minorities, the dog whistling, we know it's been happening. I'm calling it out. I want all of you to call it out, too."
The prime minister said debate around population should not be hijacked by other conversations around race or tolerance.
"We've seen what happens when these important practical debates are hijacked by these other extremist views, which occur from both the right and from the left," he said.
"I have no purchase in those agendas, I have no truck with those agendas, and I denounce them absolutely."
The peak body representing culturally-diverse Australians said cutting the annual migrant intake sent the wrong message.
Mary Patetsos, from the Federation of Ethnic Communities Councils of Australia said keeping pace with population growth and easing congestion in major cities required greater investment in infrastructure, not a reduction in migrants.
"It is extremely important that following the atrocities in Christchurch political leaders not conflate the issue of congestion with migration," she said.
"Care must be taken at this time to reassure Australians from ethnically and culturally diverse backgrounds that they belong and are welcome in Australia."
Along with cutting the annual intake, the government has also been hinting at spreading migrants across the country to ease pressure on infrastructure, without outlining any details about how this would work.
Its plan is expected to centre on forcing skilled migrants to live for at least five years in cities other than Sydney or Melbourne and enticing university students into regional towns.