Labor's promise to extend the right of parents to request a return to part-time work after having a baby is mere window-dressing, Greens deputy leader Adam Bandt says.

Prime Minister Julia Gillard announced on Sunday that Labor will legislate as soon as possible to allow new parents to ask their bosses to return to flexible and part-time work.

It follows the government's review of the Fair Work Act last year, with more announcements to come.

But Mr Bandt, the Greens workplace spokesman, says Labor is putting into law a right people already have - and it shouldn't assume his party will back the planned changes.

"Like much of what Labor is doing at the moment, such as the mining tax, it is all show and no substance," he told reporters in Melbourne.

"Labor's proposal is the right you have when you're not having a right.

"All that Labor is proposing is to put into law what people have already got - namely the ability to ask their employer for more flexible working arrangements, but if the boss says no there is nowhere to go."

Mr Bandt said if Labor was serious about giving people a better work/life balance it would support a Greens bill to give people an enforceable right to flexible working arrangements, such as exists in the UK and Germany.

"The government should not assume that they have got the Greens' support for this blatant piece of window-dressing when parents and carers around the country are crying out for better work/life balance," he said.