Staff in all publicly funded jobs who interact with members of the public will have to show proficiency in the English language under a Labour government, Ed Miliband will announce on Friday.

Outlining a major initiative to improve social integration in Britain, the Labour leader will say that every citizen should know how to speak English.

Miliband will make proficiency in the English language a key priority for a future Labour government, which would seek to achieve what he calls a "connected nation" rather than a "segregated one".

In a speech in London on Friday morning, Miliband will outline a three-point plan:

• English language teaching for newcomers to Britain will be prioritised ahead of funding for what he regards as non-essential written translation materials.

• A requirement that exists in many professions for employees to have English language proficiency will be extended to all publicly funded jobs in which staff interact with members of the public.

• Schools and parents will be encouraged to share responsibility for helping foreign-born children by including statements on English language learning within Home School Agreements.

Miliband will say: "We can only converse if we can speak the same language. So if we are going to build One Nation, we need to start with everyone in Britain knowing how to speak English. We should expect that of people that come here. We will work together as a nation far more effectively when we can always talk together."

The Labour leader insists that his focus on the promotion of English is not a "dog whistle" message designed to win over traditional party supporters who are tempted to defect to the British National Party. Miliband insists that it is a core element of his central message: that Britain needs to fashion a new integration strategy which rejects two opposing views. He rejects the ideas that immigrants should assimilate totally, by abandoning their culture, and he rejects a traditional view of multiculturalism in which communities can end up leading separate lives.

Miliband, who will be speaking after figures from last year's census showed that people of mixed race were among the fastest-growing groups in Britain, will say: "Some people say that what we should aim for is assimilation whereby people who have come here do so only on the condition that they abandon their culture. People can be proudly, patriotically British without abandoning their cultural roots and distinctiveness.

"But there is another idea we should also reject: the belief that people can simply live side by side in their own communities, respecting each other but living separate lives, protected from hatreds but never building a common bond – never learning to appreciate one another. We cannot be comfortable with separation. It blocks opportunities, leaving people at the margins. And it breeds ignorance, suspicion and prejudice."

The Labour leader, who will say that Britain is one of the few countries in Europe without a comprehensive strategy for integration, will say that the last government sometimes believed that integration would happen automatically. He will say: "Too often we were overly optimistic, thinking integration would just take care of itself; that as long as the economy was buoyant, that services were well run; that people would learn to get on together and our common life would flourish automatically. The solutions seemed abstract, but the problems were real. We talked about 'shared citizenship'. But we did too little to tackle the realities of segregation in communities that were struggling to cope."

Miliband, who will talk of the experience of his parents, who arrived in Britain as Jewish refugees from the Holocaust, will say that Britain should build a home of "richness, variety [and] diversity". He will say that Team GB's success in the Olympics highlighted this cultural richness.

"We should celebrate multi-ethnic, diverse Britain. We are stronger for it – and I love Britain for it. It gives us access to new ideas, new perspectives, new energies. Memories of the Olympics and Paralympics are going to last a very long time. But there is a lesson that stands out about our unity as a country and our diversity: people took equal pride in the achievements of all our athletes, from Mo Farah to Jessica Ennis to Zara Philips."

Miliband will say that their success has proved how "doomsayers", from Oswald Moseley to the BNP, have completely misjudged Britain. He will say: "We've had our fair share of doomsayers in Britain over the years, from Oswald Moseley in the 1930s, to Enoch Powell in the 1960s, to Nick Griffin today, who said it wasn't possible for us to get along.

"Despite our national troubles – difficult times like the riots in the 1980s and the horrific murder of Stephen Lawrence – we have generally worked together to create a more tolerant, open-minded society. In Britain today, people of all backgrounds marry across racial, ethnic and cultural divides, bring up kids, and make a future for themselves more frequently and more successfully than in many other countries."