By Sean Coughlan
BBC News education reporter, Edinburgh
A third of people on the planet will be learning English in the next decade,
says a report.
Report warns against complacency among native English speakers
Researcher David Graddol says two billion people will be learning English as it becomes a truly "world language".
This growth will see French declining internationally, while German is set to expand, particularly in Asia.
But the UK Education Secretary, Charles Clarke, has warned against the "arrogance" of English speakers who fail to learn other languages.
Learning in English
The Future of English report, launched in Edinburgh at a British Council
conference on international education, has used computer modelling to
forecast the onset of a "wave" of English-learning around the world.
In the year 2000, the British Council says there were about a billion English learners - but a decade later, this report says, the numbers will have doubled.
The research has looked at the global population of young people in education - including 120 million children in Chinese primary schools - and how many countries are embedding English-language learning within their school systems.
The linguistic forecast points to a surge in English learning, which could peak in 2010.
Speaking earlier at the same conference, Mr Clarke argued that the UK needed to improve language skills - and conceded that the country was still lagging behind in learning languages.
"To be quite candid, I'm the first to acknowledge there is an immense amount to do," said Mr Clarke. "Not least to contest the arrogance that says English is the world language and we don't have to worry about it - which I think is dangerous and pernicious."
The report's author agrees that English speakers should not be complacent because they can speak this increasingly widely-used language.
He says Chinese, Arabic and Spanish are also going to be key international languages.
"The fact that the world is learning English is not particularly good news for native speakers who cannot also speak another language. The world is rapidly becoming multi-lingual and English is only one of the languages people in other countries are learning," said Mr Graddol.
He also says that language learning numbers will decline as English becomes a "basic skill" - learnt by primary-age children, rather than something that older children or adults might want to acquire later.
Mr Graddol also warns there could be a backlash against the global spread of English and a reassertion of national languages.