The Federal Government is defending its planned IR reforms against concern that the changes will not do what they claim.

Attorney General Christian Porter is preparing to lay out new flexibility provisions that would allow employers to change employees’ duties and location of work.

The provisions were made to allow employers to get the most out of their workers under the JobKeeper pandemic support scheme, but Mr Porter is preparing to extend them to all businesses in the industries hit hardest by COVID-19.

The changes would also let employers offer part-time workers extra hours without overtime rates. Mr Porter calls it “part-time flexibility”; giving part-time workers who work at least 16 hours per week extra hours at ordinary time rates without loadings.

Australian Council of Trade Unions (ACTU) secretary Sally McManus has described it as; “Simply a way to have casuals under another name, except with lower wages”.

Unions are concerned that the provisions made under the cover of COVID-19 will be extended beyond the pandemic.

Reports say the government may offer a two-year limit on the powers to change duties and location of work to allay these fears.

The Morrison government claims that its changes will give casual workers the right to convert to permanent work, introducing a new, “clear” definition of casual employment.

It says that casuals who work regular shift patterns can ask to move to part-time or full-time employment after 12 months.

However, unions say the proposal will actually allow employers to label someone a casual even if they are hired for a permanent job. Also, they say that if casual workers want to convert to permanent work and their employer is unreasonable or does not offer them permanent employment, there is little they can do about it.

“All they are doing is removing a right for casuals if they've been exploited,” Labor industrial relations spokesperson Tony Burke has told reporters.

The new industrial relations bill will be introduced to parliament in coming days.