It has already pressed for the registration of thousands of teaching assistants and FE lecturers, but now the General Teaching Council for Wales (GTCW) wants independent school teachers to register with it, too.
The GTCW is urging the heads of Wales' 66 independent schools to help close a loophole that allows their teachers to be exempt from joining the professional body.
The situation in the principality is in stark contrast to that existing in England, where the GTC was abolished last year.
At the moment, state schools in Wales can only employ people as teachers if they are registered with the GTCW, but independent schools are free to employ unregistered teachers. Although some private schools insist on their teaching staff being registered, the majority do not.
The GTCW is calling on them to require their teachers to sign up as a condition of their employment. Currently only around 20 per cent of 1,284 teachers in the sector are registered.
"By embracing registration and regulation, an independent school will be signifying to parents that its teachers adhere to the highest standards of professional conduct and competence and conform to a rigorous code of practice," GTCW chief executive Gary Brace said. "Parents will be further reassured by the fact that registered teachers have undergone enhanced checks to ensure they are suitable to teach and have undergone proper refresher training if they have returned to teaching after an absence of more than five years."
Mr Brace said it would be safer for the public if there was a single register for all qualified teachers that could be checked by any prospective employer, ensuring all cases of professional misconduct or incompetence were dealt with in the same way.
"Insisting on this would be a badge of quality for independent schools and would help reinforce the professional status of teaching as a whole," he added.
But the proposals have split the independent sector. Emma Verrier, general secretary of the Welsh Independent Schools Council, said its members had no wish to register. Independent schools in Wales already have procedures in place to check references from previous employers, and their teachers are subject to Welsh government safeguarding regulations, she said.
Ms Verrier added that many independent schools are members of other associations that have their own codes of conduct and provide training, legal advice, professional development and support. "Therefore at this stage our members feel there is no benefit to registering with the GTCW," she said.
But Neil Roskilly, chief executive of the Independent Schools Association, said he "thoroughly supports" the idea.
"It should not be made a requirement or condition of employment, but we would encourage independent teachers to register to demonstrate their professionalism," he added.
David Neville, headteacher of St John's College in Cardiff, an independent day school for three- to 18-year-olds, encourages his teachers to register. He "strongly believes" in a single body maintaining standards for the teaching profession and wants parents to have the "greatest confidence" in his staff.
"It is not a question for us of why we do, but rather why we would not encourage staff to do so," he said. "It is not a condition of employment but no teacher not already registered and eligible to do so has ever declined the opportunity."
Under forthcoming legislation, the Welsh government is proposing to expand professional registration and regulation to cover teaching assistants, FE lecturers, work-based learning tutors and certain categories of youth workers. Eventually, all these members of staff will need to be registered with a reconstituted professional body that is likely to replace the GTCW.
66 independent schools
1,284 qualified teachers
8,929 pupils (including 1,222 boarders), down from 9,607 a decade ago
8:1 pupil:teacher ratio
Source: Welsh government's School Statistics Compendium 2012. Figures are for 2011-12.