Mandatory registration for social workers seems likely next year.
Social Development Minister Anne Tolley asked the social services select committee to inquire into the matter after the release of a discussion document that strongly suggested the change be made.
Nearly 6000 social workers are registered with the Social Workers Registration Board - but inclusion in the national registry is voluntary.
But in the last census as many as 18,000 people identified themselves as practising as a social worker.
Registration board chief executive Sean McKinley said many were practising without qualifications, police clearance or supervision.
"They do have the potential to do harm and if they're not being assessed or monitored then they may not actually realise they are doing harm as well and that's scary in itself."
The discussion paper said mandatory registration would protect the public by ensuring social workers were competent and accountable.
It said under the voluntary system, someone who had their registration cancelled for professional misconduct could continue to practice social work.
Mrs Tolley said social work was now recognised as a skilled profession.
"If they are sitting at the table with other professionals, like education or health professionals, using their skills and knowledge to help children and families, they need to be sitting with their peers.
"They need the protection of a professional organisation to back them."
She said the inquiry was necessary so that changes were sustainable, and there was cross-party support.
"I'm looking to them to make a series of recommendations to me about what should a registered social worker look like, how would we manage a registration scheme, the disciplinary process, registration process and complaints process?"
"If I'm satisfied with that then I would put a paper through Cabinet to set that on its way. We would need legislation to change that," Mrs Tolley said.
Labour's social development spokesperson, and social services committee member, Carmel Sepuloni said it was frightening that people were practising without being registered or qualified.
"Generally the members of the public look at social workers like they would nurses, teachers, other regulated workforces and assume that that's the case."
The head of Massey University's school of social work, Kieran O'Donoghue, said mandatory registration would completely overhaul the sector and allow social workers to specialise.
"In child protection, in mental health and health social work. There's a specialism in child and family support and in working with older people. They then have a career pathway."
The select committee is due to report back to the minister in September and legislation is expected to follow early next year.