LONDON — Prime Minister David Cameron returned from his tour of China with a message for Britain’s schoolchildren: Forget French and German, it’s time to learn Mandarin.

A foreign language will be compulsory in primary as well as secondary schools starting in September 2014. In most schools that means French, the language of Britain’s nearest neighbor, with German, Spanish, or Latin offered by some as alternatives.

Only 1 percent of British adults speak Mandarin well enough to hold a conversation, according to the British Council.

“By the time the children born today leave school, China is set to be the world’s largest economy,” Cameron said in an emailed statement. “So it’s time to look beyond the traditional focus on French and German and get many more children learning Mandarin.”

The government has set a target of doubling the number of people learning Mandarin to 400,000.

There will be funding for schools wanting to add Mandarin to the syllabus and a push to increase the number of speakers of the language working in schools.