Bob Lister, a Cambridge don and author of the forthcoming book Changing Classics in Schools, said Latin and Greek were likely to disappear completely from the state sector within five years if nothing was done. The number of pupils taking Latin in comprehensives this year is just 1,707.
Mr Lister said that because the time allowed to study the GCSE Latin course had decreased, it had become one of the toughest exams in which to receive top marks.
"It's not that it's necessarily more difficult," he said, "but it is more difficult in the timetable available."
He said that by making the exam easier, and shifting the emphasis away from translation from the original, schools would be more likely to retain the subject.
Classics teaching has become a "postcode lottery", Mr Lister added, with some regions entering a good number of candidates and others very few.