AUSTRALIA has enough illegal immigrants on the loose to populate a large regional city.

A Herald Sun investigation has found that nearly 60,000 people - one in every 390 - is in the country unlawfully, sparking renewed calls for a crackdown.

The 58,400 foreign citizens hiding illegally among us easily outnumber the populations of Mildura or Shepparton - Victoria's fifth and sixth biggest cities.

And they dwarf the 4700 asylum seekers who arrived by boat in 2010-11.

Documents released to the Herald Sun under Freedom of Information also reveal the biggest groups of illegals are Chinese, Americans, Malaysians, Britons and South Koreans.

More than half have been here for five or more years; 20,000 for a decade or more; and two in three have evaded authorities for more than two years. (The figures do not include visitors who overstay visas by less than a fortnight.)

Ethnic Communities Council of Victoria chairman Sam Afra said illegal residents attracted little of the outrage associated with boat people, despite taking jobs and housing, using public services, and not paying tax.

He said it was far too easy to stay here if you knew how to "work the system".

"It's shocking," he said.

"To have one in three who have been here more than 10 years (suggests) something's wrong with the system."

"Nobody's talking about it. It is a problem, and the question is, don't you think the damage justifies putting more resources in (to find them)?"

He said the involvement of illegals in criminal and other dubious activities also sullied the reputations of legal migrants.

Jailed terrorist cell leader Abdul Benbrika lived illegally for years after arriving on a visitor's visa in 1989. Three months after marrying in 1992, while still an illegal, he successfully applied to stay, living on welfare with his wife and seven children until his arrest in 2005.

Illegal immigrants have also been involved in drug cartels, sexual slavery, and fraud. Illegals accused of guarding marijuana crops in Melbourne and regional Victoria were among 43 people arrested last year in raids focusing on a $400 million crime syndicate.

A charter flight to deport 76 illegal aliens from Malaysia and Indonesia, busted picking fruit in Mooroopna last year, cost taxpayers $100,000.

Australian Human Rights Commission president Catherine Branson, QC, said it was important to remember many more overstayed visas, or arrived by plane and sought asylum, than arrived by boat.

"Another misconception is that people who arrive by boat are illegal immigrants. Australia is obliged to assess asylum seekers' claims."

There were 10,600 more illegals at June 30 last year than in 2005.