TUV leader Jim Allister has criticised the Department of Education after it emerged officials do not keep a record of working teachers who have served jail terms.
He said: "I am appalled to learn that no-one seems to either know or care how many people with criminal convictions are teaching in our schools."
In the aftermath of the disclosure that the vice-principal of a school in Londonderry was a convicted IRA spy, the MLA asked the department how many teachers in Northern Ireland classrooms had served a prison sentence.
In a written reply the department said it and other employing authorities did not hold that information.
It added: "The AccessNI Code of Practice and Explanatory Guide stipulates that, once a recruitment decision has been made, an employer must not retain Disclosure Information, or any associated correspondence for longer than is necessary. In general this should be for a maximum of six months."
Mr Allister tabled his question after it emerged that Rosa McLaughlin, appointed vice-principal of St Mary's College, Londonderry, was convicted in 1998 of IRA membership and collecting information for the Provisionals.
He said: "Teachers are supposed to be role models for children and (people) those pupils can look up to and respect. Yet, in Northern Ireland, the appointment of someone who was told by the judge at her trial that he was satisfied she would 'never be employed in the United Kingdom as a teacher' is blithely accepted."
Mr Allister added: "I believe this laissez-faire attitude will shock people across Northern Ireland. Given the sensitive, mind-shaping role of teacher it is essential that this policy is changed in order to increase public confidence in the education system."