The report commissioned by the British Council says monolingual English graduates "face a bleak economic future" as multilingual competitors flood into the workforce from all corners of the globe. A massive increase in the number of people learning English is underway and likely to peak at around 2 billion in the next decade, according to the report entitled "English Next".
More than half of all primary school children in China now learn English and the number of English speakers in India and China — 500 million — now exceeds the total number of mother-tongue English speakers elsewhere in the world.
These new polyglots, and the companies that employ them, have significant competitive advantages over their monoglot rivals, including a vital understanding of different cultures, in a world faced with rapid globalisation.
"The competitive advantage of speaking English is ebbing away," said the author of the report, linguistic consultant David Graddol. "Once everyone speaks English, advantage can only be maintained by having something else — other skills, such as speaking several languages.
"At a corporate level, the UK and U.S. economies have been enjoying a huge benefit from having so many English speakers elsewhere in the world," he told Reuters on Tuesday.
"They can outsource overseas to India, for example, allowing them to cut costs and boost growth."
But Graddol said there were mounting disadvantages for U.S. and British companies if they stayed monolingual.
Companies from other countries could use exactly the same methods to cut costs. And those foreign competitors could also trade and take orders in other languages.
"We know from trade associations that small and medium-sized British firms are losing a lot of business because they can't even answer calls from abroad on the switchboard," he said.
"Calls don't get to the right people because the telephone operators don't have the languages needed."
Around 30% of the British population speaks a language other than English, but about half of these people have that other language as a mother tongue, Graddol said.
In the United States, 22% of the population speaks a language other than English, mainly Spanish, and many of these people have Spanish as their first language, figures from the U.S. Modern Language Association show.
British higher education may already be suffering from being monolingual, Graddol suggests.
The number of foreign, particularly Chinese, students entering UK universities was falling as colleges in other parts of the world offered courses in English at lower cost, he said.
English-language teaching now earns Britain up to 1.3 billion pounds ($2.27 billion) directly and other education-related exports bring in a further 10 billion pounds a year, the report said.