Private school teachers will come under the same strict code of conduct as their state colleagues under plans put forward by the General Teaching Council for England.
The council is pressing the case for all those in the independent sector, who are exempt from registration, to sign up with the organisation.
Currently, just 9,000 teachers - from a total of more than 45,000 working in private schools - are on the council's register voluntarily. This means four out of five are not answerable to external regulation if they are accused of incompetence or unprofessional behaviour.
Keith Bartley, chief executive of the council, has met four private school associations representing almost 1,000 schools. He said registration would give schools a "quality assurance mark".
State school teachers are already governed by the council's rules. It has the power to reprimand and even strike off registered teachers guilty of professional misconduct or incompetence. It also provides members with training support.
Alan Meyrick, the council's registrar, said: "Professional registration has clear benefits for teachers, schools, pupils and to the wider public interest, no matter where teachers work.
"Our current legislative remit focuses on the state sector, but we welcome and advocate registration for the independent sector as a rounded model of quality assurance and professional support."
The independent sector has been increasingly courted by government in recent years, but remains a fierce opponent of the creeping regulation of its schools.
David Hanson, the chief executive of the Independent Association of Prep Schools, said: "The GTC came to try and persuade me of the benefits of making registration compulsory.
"I think some of our schools see it as a quality mark, but many are not persuaded. At the moment its role is seen as policing the profession, not helping it."
Mr Hanson said he supported the aims of the council, but said there would be strong resistance among his members if there were moves to force teachers to register.
Some schools saw the merits of registration because of increasing movement of staff between the sectors, Mr Hanson added.
In 2008, more than 2,100 teachers moved from the state sector to private schools, while almost 600 transferred the other way. There are also increasing links between staff in the two sectors - through academy sponsorship and other partnerships.
The GTC said it was not seeking the legislative changes needed to make the registration of private school teachers compulsory.
But John Bangs, head of education at the NUT, said private school teachers should be forced to register to stop unsuitable staff transferring into the state system without the school's knowledge.
"There is every logic in all teachers in the private sector being required to sign up," said Mr Bangs. "They should be subject to the same kinds of controls."
In October last year, the GTC struck off Michael Clarkson, a former teacher at Shrewsbury public school, for taping a pupil having sex on a school holiday.
All independent schools already have a legal duty to report staff who are guilty of serious child welfare issues to the Independent Safeguarding Authority.
GTC by numbers
- 45,000 teachers working in independent schools
- 9,000 independent school teachers registered with GTC
- 500,000 teachers registered with council
- 155 teachers referred to council for incompetence
- 682 teachers referred for misconduct.