The flood of migrant workers that has helped sustain the long economic boom has all but dried up following the COVID-19-induced closure of Australia's borders.

Migrant numbers are expected to drop by 30 per cent this financial year, and by 85 per cent in 2020-21 (compared with 2018-19).

With the economy officially in reverse and the ranks of the unemployed and underemployed swelling, there are some who say the migration slump is no bad thing.

In a recent opinion piece, Labor's immigration spokeswoman, Kristina Keneally, argued that although migration had played a key role in Australia's economic prosperity, in recent years a "cheap supply" of foreign workers had been taking jobs from Australians and undercutting wages.

"Our post-COVID-19 economic recovery must ensure that Australia shifts away from its increasing reliance on a cheap supply of overseas, temporary labour that undercuts wages for Australian workers and takes jobs Australians could do," Senator Keneally wrote.

The article provoked a strong response, including accusations of racist dog-whistling.

In an ABC RN interview the following day, Federal Population Minister Alan Tudge dismissed Senator Keneally's argument, claiming the Government had been "very, very careful" to prioritise Australians and Australian jobs through the visa system.

In making his case, Mr Tudge zeroed in a specific type of visa — the Temporary Skill Shortage (TSS) visa.

He said Australian workers are being protected by labour market testing rules, which force employers to advertise for local workers first before hiring foreigners.

The 457 visa was replaced by the TSS visa in 2018. (ABC Riverland: Catherine Heuzenroeder)

Putting to one side the merits or otherwise of the labour market testing system, Mr Tudge's claim needs context.