Social workers want the government to scrap a proposed law to make registration mandatory, saying it excludes half the country's workforce and does not do enough to protect the public.
The Social Workers Registration Legislation Bill aims to raise professional standards but still leaves it up to an employer to decide who is and who is not a social worker.
MPs hearing submissions on the bill have been warned repeatedly that leaving the definition of a social worker up to the employer will erode public confidence in the profession and result in fewer registered staff.
The Association of Social Workers supports mandatory registration, but chief executive Lucy Sandford-Reed said she was dismayed politicians had not listened.
She wants the bill scrapped and said the current system of voluntarily registration provided better coverage and protection for the public.
"If we've got 50 percent of the workforce practising outside of the legislation, or the requirement to register, it is doing nothing to achieve the stated aims of the bill which is to protect the public from harmful practice by ensuring all social workers are registered."
She planned to lobby politicians to vote against the bill at its second reading in the House next month.
In its report, the select committee noted a loophole that meant mandatory registration could be avoided if employers simply removed the term "social worker" from job descriptions and titles.
It recommended amending the bill to ensure employers explicitly use the words social worker in job descriptions.
Ms Sandford-Reed said she had identified 110 kinds of social worker roles where that job description was not used, and said just over 1500 members were employed as social workers but were not called that.
She also said she had heard of several cases where people's role was restructured just to remove the title.
"They say to the member, 'well you're not a social worker anymore, we won't pay your registration, we won't pay your external professional supervision'. The people they work with haven't changed and the type of work they are doing, hasn't changed."
The vulnerable people on the receiving end of social services deserved better, she said.
"Often these roles have been funded through government contracts from the likes of MSD, Ministry of Health, Ministry of Education, District Health Boards and Oranga Tamariki.
"So, by their very nature it means that the people using the services at a point of vulnerability in their lives and they deserve to know that the person they are working with meets the requirements for registration and is doing things like observing supervision, maintaining their professional development and upskilling themselves and that they are competent to practice," she said.
National MPs also raised concerns about the short timeframe the select committee was given to report back.
In a minority view, they noted that if the committee's 30 April deadline had been later they would have been able to pay attention to the problems raised by submitters.
National's social development spokesperson Louise Upston said the committee was unable to agree on the tasks, responsibilities and roles of a qualified social worker.
"That is something that I'm optimistic that in future the government will address," she said.
"Workforce planning, that was another issued that was raised by submitters that we want to ensure the government puts the time and effort to resolving those issues, because we need to ensure that we have sufficient social workers that are registered who are working with the most vulnerable New Zealanders," she said.
Social Development Minister Carmel Sepuloni declined to be interviewed, but in a statement said the government was committed to responding to concerns raised by social workers.