Mandate trade union is calling for on the Government to introduce “robust legislation” to get rid of “exploitative” zero-hour contracts.
John Douglas, general secretary of the union, said workers are "constantly dancing on a string" at the whim of employers.
“It is horrendous - there is a lot of pressure on workers. This system keeps them compliant. It is like contracts of a century ago,” he said.
Mr Douglas told RTÉ's Morning Ireland some employees were working up to up to 30 and 40 hours a week but did not have job certainty, which he said could lead to problems with family life.
Mr Douglas said Minister for Employment Regina Doherty needed to come up with robust proposals to plug the gaps that exist in current legislation.
He said there appeared to be “a lot of holes” in the proposed legislation and the gaps needed to be plugged.
“Anything else is just window dressing,” he said.