It does not make it clear whether the expert group will produce a public report.
Labour's confidence and supply agreement with the Greens promises to "overhaul the welfare system, ensure access to entitlements, remove excessive sanctions and review Working for Families".
Ardern said at her post Cabinet press conference that a "culture change" was needed at the Social Development Ministry so that the people at the centre of the system were treated with respect.
She made the comments in response to the most recent controversy over the treatment of a beneficiary.
It was reported yesterday that a solo mother-of-three in South Auckland was told by her Work and Income case manager that her benefit was cut because she had been on two Tinder dates.
Ardern said today that every MP had heard of mistreatment from beneficiaries in their electorates.
"I have seen too many stories as an MP in my local area which demonstrate that decisions have been made that haven't taken into account the human side of some of the cases at play.
"For instance, someone who didn't realise that they had an appointment who subsequently had their benefit cut off, who went in to seek another appointment immediately in order to rectify the situation only to be told the books were full and that they would have to come back in several weeks.
"These kinds of decisions have huge ramifications for people and their lives."
Many case managers "do an exceptional job", she said, while adding that "in some situations you are left wondering why there just wasn't the respect shown that should have been".
Social Development Minister Carmel Sepuloni is reviewing the welfare system and the results of her work were "imminent".
Ardern said sanctions were one of many issues that the review was considering.
She noted that the sanctions imposed on beneficiaries were one of the key issues of concern raised by a UN Committee in Geneva last month.
Former Green co-leader Metiria Turei was the most vocal proponent of getting rid of some of the punishments, in particular a provision which halted payments to solo mothers who did not reveal the identity of their child's father.
National's social development spokeswoman Louise Upston said it was only right that in return for access to benefits, people met obligations including looking for work, turning up to appointments, staying drug-free and being honest about living arrangements.
"It's the clear expectation of taxpayers that if beneficiaries are not doing that, then there should be sanctions," she said in a statement.
"This is not 'beneficiary bashing'. This is simply us wanting to make sure that every New Zealander is achieving their potential and that's done by getting out of dependency."
