Shay Kernaghan, a business studies tutor in a London Muslim school, told Southwark Crown Court he would never have behaved in that way.

He said forensic traces found on two school chairs were from after-school sex acts with fiancee Tracey McNally.

Mr Kernaghan, 27, who lives in County Tyrone, denies eight sex charges.

He said some pupils had reached the wrong conclusions from instances which had included him reaching into his pocket for cold sore cream.

Strict approach

"I can understand them coming to that idea, but what I can't understand is them pursuing it," he said.

He said he could only think they pursued the matter through spite and malice because of his strict approach to discipline.

The court had earlier heard from a former pupil how Mr Kernaghan "prepared himself" by putting chairs either side of him to hide what he was doing.

One told how it left her feeling sick and another said she was terrified and embarrassed.

It is claimed Mr Kernaghan "abused a position of trust" by "engaging in sexual activity other than sexual intercourse" at the London school.

It is also claimed he "committed an act of lewd, obscene and disgusting nature, outraging public decency."

The alleged incidents are said to have taken place between 1 October and 12 December 2003.