Britain must "work at" becoming a more integrated society, Ed Miliband has said as he outlined plans for a "comprehensive strategy" to deal with the pressures of a multi-ethnic society.
The Labour leader admitted his party had failed to control immigration or deal with racial and ethnic segregation in Britain's cities during its last spell in government.
He vowed not to sweep "deep anxieties" about the impact of immigration under the carpet and signalled that he was prepared to "look at" the impact of a Government cap on immigration from outside the EU - a policy he has heavily criticised.
But he hailed the London Olympics as a symbol of the successes of the UK as a diverse community and set out measures on language, housing and the workplace to help strengthen it further.
In a speech in Tooting, south London, Mr Miliband received loud applause when he insisted that contrary to what figures such as the blackshirt Oswald Mosley, Enoch Powell and BNP leader Nick Griffin suggested, the multi-ethnic Britain shown in this week's census and in the summer's Olympic and Paralympic Games was a cause for celebration.
Drawing on his own parents' experience as Jewish refugees from the Holocaust, Mr Miliband said: "We should celebrate multi-ethnic diverse Britain. We are stronger for it - and I love Britain for it. Britain is at its best when it comes together as a nation, not when it stands divided. That's what One Nation is about.
"But at the same time we know there is anxiety about immigration and what it means for our culture. The answer is not to sweep it under the carpet or fail to talk about it, nor is it to make promises that can't be kept. It is to deal with all of the issues that concern people."
Mr Miliband accepted that there are concerns about the "pace of change" in British life due to immigration, particularly in specific areas which have witnessed high numbers of new arrivals.
"The capacity of our economy to absorb new migrants has outrun the capacity of some of our communities to adapt," he said.
"The last Labour government made mistakes in this regard. We have said we will learn lessons from eastern European migration and ensure maximum transitional controls in future. And we will look at how the Government's immigration cap works in practice. But I believe we can all cope with these pressures if we recognise them and understand how to respond."