Two billion people, a third of the population of the planet, will be learning English in the next decade giving it the full status of the "world's language", a research report published Thursday reveals.

Although the surging number of English learners could peak in 2010, by 2015 half of the world's population could be speaking English, says "The Future of English" report produced by the state-funded British Council.

This growth will see French declining internationally while German is set to expand, particularly in Asia, said researcher David Graddol, who added that Chinese, Arabic and Spanish are also going to be "key international languages" of the future.

"The world is rapidly becoming multi-lingual and English is only one of the languages people in other countries are learning," Graddol said in a BBC interview.

The report looked especially at how countries around the world are including English-language learning in their school systems.

The report expects the boom in English learning to be over by 2050 as English becomes a "basic skill" learnt by primary-age children rather than a language older children or adults might want to learn later.

When English becomes a basic skill, the number of people needing to learn English around the world may slump to just 500 million, says the report which also warns that there could be a backlash against the global spread of English and a reassertion of national languages.