Exam boards could face losing their contracts after chief examiners were secretly recorded advising teachers about what questions students should expect in their GCSE and A-level papers and how they should answer them.
An investigation found that teachers were paying up to £230 to attend seminars in which they were offered explicit advice on the parts of syllabuses they should concentrate on and which sections they could afford to ignore.
The Education Secretary Michael Gove has ordered an official inquiry into the exams system after one examiner was taped admitting they were "cheating" by revealing which questions would be appearing.
During the meeting, Paul Evans, of the WJEC exam board, told attendees which of several topics would feature in a compulsory history GCSE question, before admitting: "Probably the regulator will tell us off."
The findings by The Daily Telegraph will lend weight to the notion that competition to win business from schools has led the main boards – AQA, Edexcel, OCR and WJEC – to offer too much guidance to teachers to help improve results and win more trade.
The percentage of passes at top grades has increased in each of the past 23 years, prompting criticism that "grade inflation" is making exams less useful to employers and universities.
A spokesman for WJEC said Mr Evans was merely confirming "long-standing guidance" on exam questions. He added: "The alleged use of the word 'cheating' appears to have been injudicious, as well as inaccurate; we shall investigate this further."
However, Mr Gove signalled that the central inquiry could potentially spell the end for the boards setting GCSE and A-level papers, saying the Government would "take whatever action is necessary to restore faith in our exam system".
He added: "Nothing is off the table. Our exams system needs fundamental reform. Today's revelations confirm that the current system is discredited."
Mr Gove said he had asked Glenys Stacey, the new chief executive of the exams regulator Ofqual, "to examine every aspect of the exam boards' conduct which gives rise to concern and to report back to me within two weeks with her conclusions and recommendations for further action".
Ofqual said the exam boards "must meet to make sure their commercial activities do not impact on the standards and integrity of qualifications" or they would face regulatory action.