A "cheating scandal" has engulfed three of Britain's top three public schools amid claims that pupils were given a heads-up about questions in upcoming test papers, it has been reported.

Winchester College has nullified exam results for 13 students amid claims they were given advance knowledge on two exam papers.

The exclusive school, which charges £31,000 a year per pupil, has suspended its head of art history, Laurence Wolff, 56 in connection with the claims he gave students "prior information on exam questions on two papers", the Daily Telegraph reported.

The exam board, Cambridge International Examinations (CIE) is investigating Charterhouse School, which charges up to £36,000 a year for boarding students, over claims pupils knew questions ahead of an upcoming exam.

The CIE said there was no evidence of wrongdoing by Charterhouse which denies any student was guilty.

However it comes only days after Eton College, with fees of around £32,000 a year, fired its head of economics, Mo Tanweer, after claims that students got information about an economics paper.

At the centre of the controversy are concerns over a possible conflict of interest as teachers in the Eton and Winchester cases were also examiners for the Pre-U exams which independent school pupils take as A-level equivalents/

Former Wellington College headmaster told the Telegraph how: "there needs to be an iron wall between the setting of these exams and the way they are marked".

The controversy at Winchester College was revealed after it emerged that pupils from the school had been discussing the contents of the upcoming exam online. There is no suggestion pupils or other members of staff at any of the schools are culpable of wrongdoing.

Tim Hands, headmaster at Winchester College, said: "The College has treated this matter very seriously, and has worked closely with the examination board throughout. It greatly regrets what has happened. No boy was to blame for the exam irregularity, and the board used standard procedures to award final grades."

Charterhouse passed on concerns to the CIE that pupils had been given details of an upcoming paper via social media. A spokesman for the school said: "Charterhouse staff were made aware of concerns raised by pupils and referred the matter to Cambridge International Examinations (CIE) at the time.

"We have been assured by CIE that our pupils have not been affected. All Charterhouse pupils who sat the CIE Pre-U Economics examinations were awarded their marks for the papers in the normal way."

Ofqual, the exam regulator is also involved in the investigation. A spokesperson for the Department of Education told the Telegraph: "Parents and students must be able to have faith in the exam system. Any suggestion of malpractice is concerning and should be looked into.

"Cambridge International Examinations board are dealing with the incidents ‎and have made the exam regulator Ofqual aware."