Teachers' leaders warned that the UK was "losing a generation of linguists" after the number of GCSE students taking modern languages plummeted.
French and German were the biggest casualties of all the major subjects, with the number of exam entries down 14.4 per cent and 13.7 per cent respectively since last year.
The figures were even lower in the year-long language GCSE Short Courses, where numbers dropped by 49.8 per cent in German and 42 per cent in French.
The huge fall coincided with the first year of modern languages being optional after the age of 14.
John Dunford, general secretary of Secondary Heads Association, said things were likely to get worse because yesterday's figures represented the last batch of candidates for whom taking a language was compulsory.
He said: "These figures, from a year before modern languages became voluntary for 14 and 15-year-olds, are very bad news, not least for the future of this country as a trading nation. We are losing a generation of linguists."
Mr Dunford said he would be writing to the Government to urge them to rethink their decision to allow students to drop modern languages.
Figures released by the Joint Council for Qualifications listed 272,140 entries for French in 2005 compared with 318,095 in 2004. There were just 105,288 exam entries in German this year, compared with 122,023 last year.
In the GCSE Short Courses - which are equivalent to half a GCSE - there were 769 entries in German for 2005 compared with 1,533 the year before and 3,352 in French this year, down from 5,775.
Short courses in Spanish also suffered, with exam entries in 2005 numbering 1,374 compared with 1,591.