Parliament has united in supporting Green MP Sue Bradford's bill to extend the amount of time a mother in prison can spend with her baby.

There was no opposition to the legislation passing its first hurdle and it will now go to a select committee for consideration.

National MP Katherine Rich says the concept makes sense. She says a baby does not know it is in prison, but it does know it is warm and fed and in the arms of someone who cares. Mrs Rich says she cannot help but think that some babies will be a lot safer in prison "mother and baby units" than in homes where they will not be cared for.

Under the current law, babies of women in prison are usually removed from their mothers at around six months. The new legislation would extend that to two years.