Asked by Mike Hosking on NewsTalk ZB this morning whether she would support the bill Ardern said she hadn't looked at it.
"To be honest I haven't looked at the detail of that individual member's bill."
Ardern said Labour, the Greens and New Zealand First had all put forward private members bills.
She couldn't say whether the proposal had been raised in coalition talks without looking at the bill.
"I wouldn't give you a hard and fast answer right now."
But Ardern said she wanted everyone to be in KiwiSaver.
"Do we want everyone to be in KiwiSaver? Yes. Of course there are different ways to encourage that."
She said discussions around compulsory superannuation saving had been around for a long time.
In the past there had been ways to encourage more KiwiSaver engagement but she said some sweeteners that past governments had removed had reduced people's likelihood to engage with the scheme.
The National-led government removed the $1000 kick-start payment which all new members received and halved an annual member tax credit from $1043 to $521.
Labour has yet to release details of its KiwiSaver plans other than to say it wants to get all workers into the scheme and increase the minimum contribution rate from 3 per cent to 4.5 per cent.
The government already owns a KiwiSaver provider. Kiwi Wealth is owned by Kiwi Group Holdings which is owned by the government, ACC and the NZ Superannuation Fund.
There are no restrictions on where it can invest but it does have a socially responsible investment policy.