The casualisation of Australia's workforce has resulted in a "crisis of insecure work", unions say.

Speaking at the launch of a national campaign against the spread of casual and contract work, Australian Council of Trade Unions (ACTU) secretary Jeff Lawrence said more workers than ever were employed on an "insecure basis".

Jeff Lawrence ... says there are more casual workers each year.

"What we have in Australia now is a crisis of insecure work," he told union members in Sydney today.