The General Teaching Council heard that Dr Michael Aldersley, 53, admitted saying the words in November 2000 at Calderstones comprehensive in Liverpool, but insisted he did not intend them to be racist but to mean “foolish and silly children”.

The disciplinary order will remain on his teaching record for two years, but he can continue teaching.

Ruling in Dr Aldersley’s absence, Mick Carney, the disciplinary panel chairman, said: “Teachers should always be aware of the likely impact of language used in the classroom.”

A three-member panel heard how Dr Aldersley opposed the apartheid regime while teaching in South Africa during the 1970s.

During a computer skills class he told the 14-year-old pupils: “Everyone in the nig-nog corner: come here, you might learn something.”

After an investigation following complaints from the pupils and their parents, Dr Aldersley was sacked for gross misconduct in May 2001. Headteacher Brian Davies said Dr Aldersley, who had taught at the school for 10 years, apologised to pupils as soon as he realised his remarks had caused offence.

Mr Davies said he considered the phrase to have only one, derogatory meaning towards black pupils.