The UK has an "alarming shortage" of people able to speak the 10 languages vital to our future prosperity and global standing, warns a report.
Schools should teach a wider range of languages, with language skills given the same status as the sciences and maths, argues the British Council.
More adults should learn at least one new language, say the authors.
Failure to act risks the UK losing out "both economically and culturally", said John Worne of the British Council.
"The problem isn't that we're teaching the wrong languages, because the most widely taught languages like French, Spanish and German all feature in our top 10.
"But the UK needs more people to take up the opportunity to learn and, crucially, get using these languages, along with new ones like Arabic, Chinese and Japanese", said Mr Worne.
The authors analysed a range of economic, political, cultural and educational factors to define the languages which "will be of crucial importance for the UK's prosperity, security and influence in the world over the next 20 years".
A YouGov poll of more than 4,000 UK adults found that three-quarters (75%) were unable to speak any of the 10 languages well enough to hold a conversation.
Some 15% of the UK population said they could hold a conversation in French but only 6% said the same of their German skills, 4% could converse in Spanish and 2% in Italian.
The other languages on the top 10 list were spoken by 1% or fewer of the population, the poll suggests.
The report was endorsed by Martyn Heather, head of education at the Premier League: "Being able to speak another language opens up a world of opportunities to play and coach in football leagues across the globe.
"It is the people who understand languages and feel confident with other cultures who will be able to make the most of these opportunities and thrive the most overseas".
Earlier this year the British Council challenged everyone in the UK to learn at least 1,000 words of a new language.
In his foreword to the report Mr Worne stresses that it is functional skill rather than fluency that counts.
"'Fluent' is an inhibitor, 'functional' is a liberator.
"It begins with a few words and phrases and that small investment can grow into a lifetime of interest, employment and opportunity," he writes.
The report urges the four UK governments to link their language teaching policies more clearly to their aspirations for international business, education and culture.
Greater use should be made in education of the language skills of minority communities within the UK, while businesses should invest in the teaching of languages from which they will directly benefit, say the authors.
A spokesman for the Department for Education in England said the introduction of the new EBacc was "reversing successive annual falls in the number of entries to modern language GCSEs since 2002.
"There were 50,000 more entries to languages GCSEs this year, with French up 16%, German up 9% and Spanish up 26%.
"From next year it will be compulsory for children to be taught a foreign language from age seven through to age 14," said the spokesman.