Forcing overseas trained teachers and instructors without UK qualifications to register as teachers could open the door to untrained staff being treated as teachers, the NUT warned this week.
The Government has announced plans to give around 11,000 overseas teachers and instructors without qualified teacher status provisional registration with England's General Teaching Council from this September.
Official consultation documents on the proposals say that registering unqualified staff will be "reassuring to parents, who may not be able to distinguish between those who are qualified teachers and registered with the council and those who are unqualified teachers".
But the NUT says this is misleading, as teaching assistants and cover supervisors, who are also carrying out some teaching work, would not be obliged to register.
John Bangs, head of education at the union, welcomed moves to provisionally register the 34,000 trainee teachers starting PGCE and other courses each year. But he said: "If you start registering other forms of unqualified teachers there is a blurring of the lines. Where does an instructor stop and a higher level teaching assistant begin?"
An NUT submission on the proposals said: "The consultation document appears to imply that registration with the GTC, rather than qualified teacher status, is essential for the quality of educational provision, which is not the case."
But the Government said that plans to register trainee and unqualified teachers would "enhance the professionalism of the wider teaching workforce."