Fears have been raised that a bill to make registration mandatory for social workers will be too easy for employers to get around.
Although there is widespread support for a rule that says social workers must be registered, many are urging the government to rethink its approach.
The bill essentially leaves it to an employer to decide which jobs will be called social worker positions.
The Association of Social Workers chief executive Lucy Sandford Reid said she had already heard from members who suddenly had their job descriptions changed.
"I'm now no longer called a social worker," one person told her.
"I'm now called a navigator, whānau ora worker, family worker, allied health worker, and my employer is now not funding my external supervision, is not going to support the renewal of my practising certificate, is not going to support my professional membership," she said.
A practising certificate costs $368 a year.
PSA organiser Amy Ross said the proposed bill was too loose and allowed employers far too much leeway.
"You can have over-qualified people who are being underpaid and aren't actually having any compensation for their employer for registration or professional development.
"And vice versa people could think that they're actually interacting with a social worker and think that they're getting somebody regulated, qualified, professional, and actually what they've got is someone who doesn't have any training or skills at all," she said.
Rather than defining social workers by a job title, critics said the government should introduce a scope of practice which outlines the tasks, responsibilities and the roles which a qualified social worker is expected to carry out.
Capital and Coast DHB professional leader for social work Kim Myhill said that was the approach taken by other health professionals such as physios and occupational therapists.
"They have a professional board and those boards have got definitions and scopes of practice, that clinicians are expected to work to that defines the work that they do," she said.
"Social work at this time doesn't have that clearly set up."
Critics rejected the previous government's claims it would be too difficult to define social work, and said an international definition already existed.
Amy Ross said the reluctance to introduce a scope of practice came down to money.
"If you leave it to the employer, they will essentially be entitled to have people do the same work they do now as social workers, but be called something different and therefore not attract the equal pay rate that we hope to win for social work."
The Social Services Select Committee is due to report back at the end of March.