Britain’s “multi-culty Balkanisation” of society, in which primary school children have been taught in their parents’ language, has led to a disaster in which many UK citizens cannot speak English, Boris Johnson has said.

The London mayor, who was speaking on his LBC phone-in, expressed some sympathy for the announcement by Nigel Farage that staff in public services should show they can speak English.

Johnson said: “We went through a long period in Britain of having kind of multi-culty Balkanisation of our society. We thought it was a very good idea to teach kids in their own language in primary school classes in London. That is a disastrous approach. They should be learning in English.”

The mayor said that city hall had dropped the automatic translation of official documents into “umpteen languages”. He stopped short of echoing Farage’s suggestion that public service staff, particularly those working in the NHS, should show they can speak English. But Johnson said he was amazed by reports that some NHS staff could not make themselves understood in English.

He said: “Everybody who comes to London, everybody who comes to work in our economy, should be able to speak English … If you go to Tower Hamlets, you can find people who have been there for several generations who still don’t speak English.

“The media is so massive now, so diverse that people can be tuned in to their own communities and not feel the need to learn the common language of this city and this country. That is a great, great shame. It is a huge wasted opportunity for them. I think everybody in this country, particularly people working in our public services, should speak English.

“I am amazed by reports that people cannot make themselves understood in English in this country to people in the NHS. That is completely wrong. I am sure NHS managers will be taking steps to sort it out. I think we should have a culture in this country that if you come here, you do as the Romans do: you learn English and you speak English. I don’t mean this in a punitive sense. This is a wasted opportunities for these families.”