Unions not invited to participate in the independent panel that will review the 457 skilled migration visa have criticised the body as being ''stacked''.

As Immigration Minister Scott Morrison brushed aside suggestions that he had opened the way to a flood of new skilled migrants on 457 visas, the unions increased criticism of the panel.

The panel comprises John Azarias of Deloitte Australia, Peter McDonald of Australian National University, Katie Malyon of Ernst and Young and Jenny Lambert of the Australian Chamber of Commerce and Industry.

The panel was established to review the four-year visa for foreign skilled workers after the Labor government made sweeping, and restrictive, changes last year.

Some of the panellists have openly spoken about labour market testing; one aspect of the 457 visa requirements is that companies must first test the local labour market to ensure there is no suitably qualified and experienced Australian citizen, or permanent resident, to fill that position.

Mr Morrison told Sky News on Wednesday the changes were about ''regulation reduction removing union red tape which was put there by the previous government''. But unions argue the removal of the labour market testing will hurt Australian workers.

In a letter obtained by Fairfax Media, Assistant Immigration Minister Michaelia Cash wrote to ACTU president Ged Kearney after she complained about the members of the panel.

''The government respects the important role unions play in the community,'' she wrote. There was no mention of the unions being represented on the panel, but that the independent panel would ''carefully consider any submission made''.

The Australian Workers' Union assistant national secretary Scott McDine said it was ''incomprehensible'' that you could have a review of 457 visas and exclude trade unions from the process. ''The review . . . has been stacked to deliver a predetermined outcome that will hurt Australian workers,'' he said.

Opposition immigration spokesman Richard Marles said the program ''should not [be] a mechanism to replace Australian jobs''.

Consult Australia chief executive Megan Motto said ''the 457 visa by its very nature should be flexible and responsive to the needs of business''. Ms Motto's consulting team has 280 member firms with 54,000 staff.

The executive director of the Australian Mines and Minerals Association, Scott Barklamb, slammed the unions for using scare tactics.

''The resource industry is not a large user of skilled migrants, but we do welcome any move to ensure that when employers do need to access overseas skilled labour, they cando so through an efficient and responsive system,'' Mr Barklamb said.