The Government's being urged to head back to the drawing board on zero hour contracts.

Workplace Relations Minister Michael Woodhouse has unveiled new legislation aimed at stamping out instances where employers don't commit any hours of work, but expect employees to be available when required without compensation.

But Council of Trade Unions Secretary Sam Huggard thinks the proposed changes actually make zero hours contracts more likely.

He said while they stipulate the employer needs to reimburse a worker for being available, the law doesn't specify a minimum rate.

"The compensation's not set out in any particular way, it could be just a tiny amount of a few dollars...it's meaning that there's no real extra protection here for workers under these proposals."

Mr Huggard said that means someone could be required to be available to work 24 hours a day 7 days a week, and only be reimbursed a small amount.

He said the proposed changes might actually increase their use.

"The only real safeguard that's available for workers is a compensation in order to be on a zero hour contract really."