Melbourne will stop tomorrow and the nation will watch as the city pays its respects to an Italian-born cafe proprietor whose death at the hands of a deranged assailant has rubbed raw a debate about immigration numbers, refugee intake, ethnic crime and Islamist-inspired terrorism.

Whether we like it or not those issues are conflated in the public mind along with concerns about overcrowding and infrastructure bottlenecks in Sydney and Melbourne.

What is not in dispute is that Sisto Malaspina was the victim of a random act of terror on the streets of Melbourne.

Whether assassin Hassan Khalif Shire Ali was radicalised by Islamist ideology, or simply alienated and under the influence of drugs, is less relevant than the broader question of what is to be done to maintain community support for a non-discriminatory immigration program.

This includes the country’s acceptance of its fair share of refugees from places ravaged by war and famine – 68.5 million refugees globally, according to the United Nations High Commissioner for Refugees. Ali himself was from war-torn Somalia.

Poll numbers foreshadow eroding support for the immigration program. A mid-year Newspoll found that 72 per cent of those questioned – up from 56 per cent earlier in the year – favoured a reduction in numbers. A Fairfax-Ipsos poll published on Monday finds that 46 per cent believe the number of immigrants from Muslim countries should be reduced, 14 per cent say it should be increased, while 35 per cent believe it should stay the same.

Failure of the political class to address the immigration issue – except surreptitiously by imposing a “ceiling’’ on net overseas migration (NOM) rather than a target in this year’s budget – plays into the hands of demagogues on the right.

That NOM number of 190,000 has remained unchanged for seven consecutive years. It should be scaled back significantly.

Given congestion and housing affordability pressures, one can hardly blame New South Wales Premier Gladys Berejiklian for convening an expert panel to assess population. In reality, population is a federal responsibility.

Leaving aside the discreditable behaviour of Prime Minister Scott Morrison and Victorian State Opposition Leader Matthew Guy, who descended on Pellegrini’s coffee shop for a photo-opportunity to extract political advantage from human tragedy, Malaspina’s death should encourage a root and branch conversation about the costs and benefits of Australia’s immigration and refugee intake programs.

An Australian Parliamentary Library research paper, Budget Review 2018-19 Immigration, points out that in the 2017-18 budget, Australia’s projected net overseas migration(that is, the gain or loss of people arriving or departing Australia) was 209,018, but the actual NOM was 242,600. That was 16 per cent up on the projection. Net overseas migration accounts for about 60 per cent of the country’s population growth.

These numbers do not include the more than 300,000 people who arrive in Australia annually on temporary visas, including international students, working holiday-makers and temporary workers. Many of these temporary arrivals gain permanent residency as a pathway to citizenship, boosting NOM numbers in the process.

This bulge settles predominantly in Sydney and Melbourne, fueling community concern about quality-of-life issues.

What is needed, therefore, is an upfront discussion about whether an immigration program that is causing Melbourne and Sydney to burst at the seams, and a refugee intake that is stretching the ability of support services to cope, is in the long-term national interest.

In Melbourne, whether they admit it or not, police are being run ragged in their efforts to combat ethnic crime.

Numbers tell their own story. Attention has focused on the Sudanese population, given that its young people figure disproportionately in crime statistics.

While it is true that Sudanese, who account for 0.16 per cent of Victoria’s population, represented just 1.07 percent of offenders in 2017-18 compared with 71.25 per cent of Australian-born, the incidence of Sudanese crime is unacceptable.

Sudanese criminal offenders rate six times higher than their population share. In aggregate terms, people of Sudanese origin rank second in aggravated burglary offences, third in serious assault, third in car theft, second in aggravated robbery and third in riot and affray.

Out of political considerations and under pressure from a business lobby whose mission is to jam as many people into the country as possible, both government and opposition are strangely reluctant to address community concerns about immigration.

What is clearly required is a comprehensive and independent review outside the parliamentary process of what might constitute an ideal population size and composition, including the refugee component.

Personally, I am for an increase in the refugee intake on humanitarian grounds since Australia lags behind comparable countries in its acceptance of refugees under a program administered by the UNHCR.

But these refugee intake programs need to be more carefully designed than has been the case, and resources made available to ensure new arrivals are properly absorbed. Clearly, this process has been deficient.

As part of such a review government and opposition should also reconsider their resistance to ending the incarceration of boat arrivals on Manus Island and Nauru. An amnesty should be considered.

Holding asylum seekers hostage indefinitely to Australian domestic politics is shameful. A mealy-mouthed Labor Party is no better than the government in this regard.

We should be better than that.