Mark Hutcherson, 43, who works at Bettws comprehensive, Newport, was fined pound;300 by a court in August 2004 after pleading guilty to assault causing actual bodily harm.

He was called before the General Teaching Council for Wales (GTCW) for a conduct hearing last week to assess if he was fit to carry on teaching after his conviction for the assault on Julie Collins.

Mr Hutcherson told the Cardiff hearing that he pulled clumps of hair from Miss Collins’s head and slapped her face after a drink-fuelled row last year.

He said he had been subjected to prolonged abuse from Miss Collins and finally snapped after learning she had slept with another man. They had broken up months before but had been talking about getting back together.

“Obviously I’m ashamed of what I did. I admit they were nasty injuries but I was in an extreme state of mind,” he said.

Miss Collins had told police in a statement before the court case that she had been severely beaten. In the statement, read out at the GTCW hearing, she said that her ex-boyfriend had sat astride her, grabbed and yanked her hair, punched her and put his hands around her neck.

“I couldn’t breathe and thought I was going to die,” she said.

PC Dean Williams, who had dealt with the case, confirmed at the hearing that Miss Collins’s injuries seemed more severe than Mr Hutcherson’s account had suggested.

Damien Phillips, for the GTCW, said: “We are living in an age where assaults in schools are growing and becoming increasingly more violent. I ask what message Mr Hutcherson is giving to his pupils. What he did was wrong and cannot be condoned.”

But Mr Hutcherson told the hearing he did not think the incident affected his role as a teacher.

He said: “I am of previous impeccable character. I have an excellent track record. What happened was in my private life. I take my job seriously and professionally. I still think I have a lot to contribute to the children.”

Sheila Drayton, chairing the conduct hearing, said that Mr Hutcherson’s actions could not go unpunished.

“The teaching profession is one that must be held in high regard. Teachers are role models for their pupils, therefore your crime is relevant and your conduct was unjustified,” she said.

“But we are not satisfied that the injuries sustained by Miss Collins were as severe as some accounts suggested.

“We are also impressed by your honesty in your admission of guilt and your recognition of your wrongdoing.

“We hope you will continue to enjoy a fulfilling career as a teacher.”

Mr Hutcherson was given a reprimand which will stay on his record for two years.

Bob Meier, head of Bettws high school, said it had carried out its own internal investigation into Mr Hutcherson’s case and found no evidence of any similar incidents occurring in school.

“We felt that because of Mr Hutcherson’s exemplary record in school, no further action would be taken, subject to the General Teaching Council’s recommendations,” he said.