The Qualifications and Curriculum Authority found that more than 4,500 candidates were penalised for malpractice last summer, an increase of more than a quarter (27 per cent) on 2004. Of these, about 1,100 candidates were caught smuggling mobile phones into exam rooms.

If caught, students can face disqualification from all or part of their exams or have their overall mark reduced. But not many penalties were handed out - one in every 1,500 results, about 0.06 per cent of the total.

The QCA’s annual report said: “The most common type of malpractice, accounting for about two-fifths of the total, was the introduction of unauthorised material into the examination room, and around three-fifths of these cases related to mobile phones or other electronic communication devices.”

About a third (1,414) of the 4,500 penalised candidates were found to have been involved in plagiarism, collusion or copying another candidate’s work in their exams or coursework.

Students were also penalised for exchanging suspicious information (435 students), disruptive behaviour (300), altering results documents (13) or impersonating someone else (9).

Other offences included using obscene material in exams or coursework (208), failing to follow invigilators’ instructions (133), deliberate destruction of work (10) and theft of work (7).

Ken Boston, QCA chief executive, said: “As we enter the summer exam season, I have today written to schools and colleges to remind them of their responsibilities to impress upon students the importance of not taking mobile phones into examinations.”

The QCA’s second annual report found that the three exam boards - AQA, Edexcel and OCR - provided a satisfactory level of service to schools and exam centres.