A sharp decline in entries to modern foreign language A-levels has been blamed by head teachers on severe funding pressures.
Entries to A-levels in French have dropped by 6.4% from last year, in German by 4.2% and in Spanish by 2.7%.
Malcolm Trobe of the ASCL heads' union said schools and colleges were finding it hard to run courses with small pupil numbers, due to funding shortages.
The government replied that it had been encouraging pupils to take languages.
This is mainly through the English Baccalaureate - the wrap-around qualification which requires pupils to sit a range of certain GCSES including a language.
The claimed effect of funding shortages comes as pupils in England, Wales and Northern Ireland are receiving their A-level results.
But Mr Trobe, interim general secretary of the Association of School and College Leaders (ASCL), said he was worried about the "continuing decline" in the number of A-level entrants in modern foreign languages, and other "minority" subjects such as music, and design and technology.
"These statistics reflect the fact that sixth forms and colleges are finding it increasingly difficult to run courses where there are relatively small numbers of students because of severe funding pressures," he said.
"The level of post-16 funding is woeful and urgently needs to be addressed.
"We are in danger of becoming trapped in a vicious circle where entries to these very important subjects continues to decline and there are consequently fewer people to teach them in the future, exacerbating an ongoing recruitment crisis," he added.
Mr Trobe also said changes to the AS-level - which do not now count towards the final A-level grade - had also effectively narrowed pupils' choices.
In the past, pupils had generally been allowed to take four subjects and then drop one at the end of the first year, he said.
Now, he argued, "we are just reducing curriculum choice, full stop."
National Association of Head Teachers general secretary, Russell Hobby, said that while it was "good to see an increase in the top grades awarded in modern foreign language", a national strategy needed to be implemented to address the drop in entries.
He said: "Yet again we see a decrease in the number of students taking these subjects."
"We need to ensure that there are enough trained teachers to offer a breadth of languages, and for schools to be supported to ensure primary pupils are also exposed to the challenges of learning a language," he added.
Schools minister Nick Gibb acknowledged that the drop-off in foreign languages was a "worry".
"There has been a slight decline in modern foreign languages but the introduction of the EBacc has arrested the historic fall of foreign languages at GCSE and we expect this will grow the pool of young people who are equipped to go on to study languages at A level."
The Department for Education said it was protecting funding for 16- to 19-year-olds and ended the unfair difference between post-16 schools and colleges.