Prime Minister Scott Morrison is proud there are more people in work than before the pandemic began, but the vulnerability of gig and casual workers remains hidden, a parliamentary committee heard on Tuesday.

"People are coming to this committee and telling us they are the working poor," Labor senator Deb O'Neill said.

"That they don't know how they're going to put food on the table, that they cannot make the next rent payment, despite working three jobs as casual workers across multiple sites in aged care."

Industrial Relations Minister Michaelia Cash said she was wary of reforms that could stifle innovation, limit flexible work and raise prices in the gig economy.

But Labor senator Tony Sheldon said some food delivery workers, the "heroes of the pandemic", are now getting as little as $6.67 an hour, with no worker's compensation or superannuation.

Part-time workers also took the biggest hit during the first COVID-19 lockdowns.

Senior government official Alison Durbin confirmed 58 per cent of growth in employee numbers since May this year have been casuals, after they took a massive hit at the onset of COVID-19 lockdowns in March 2020.

The assistant secretary of the attorney-general's department said 72 per cent of the decline in employee numbers overall in the depths of the pandemic were casual workers.

Yet the lack of specific official data on vulnerable gig workers and freelancers could leave parliament blind when it comes to new laws dealing with insecure work and its lack of paid leave and other benefits.

"There is no international or domestic definition of insecure work," Ms Durbin said.

And while independent think-tanks point to the increasing casualisation of the workforce, casual employment has been stable for decades at around a quarter of the workforce, according to the Australian Bureau of Statistics.

ABS data also shows 7.3 per cent of part-time workers would prefer to work full-time and are available to start now.

Senator Cash said fair work legislation passed in March provided a pathway into more permanent jobs, via "casual conversion" measures.

She said it was disappointing the full suite of measures didn't get through and confirmed they remained on the federal government's workplace agenda.

"Strong protections" were in place for gig workers, including food delivery workers, many of whom are independent contractors, she said.

Courts can intervene where the contracts are found to be "harsh or unfair" and to act against coercion.

The government committed $2.8 million last December to improve its collection of labour market data.

Australian Associated Press