At Thursday's launch of the new Commission for Integration and Cohesion, which will report to her, Ms Kelly will recognise that the August 10 terror alert heightened tensions in some areas.
She wants the commission to consider tough questions, such as a request by Muslim groups for Islamic festivals to become bank holidays. The speech, to be made in London, will reinforce the message delivered by the home secretary, John Reid, earlier this month rejecting the idea that "anybody who talks about immigration is somehow a racist".
Ms Kelly will recognise the "proud tradition" of inclusion and cohesion in Britain but say a new and complex set of challenges are presenting themselves. "All of that history matters, all of it is relevant," she will say. "But for me what is more important is that the landscape is changing before our eyes and for some communities life in Britain feels different today than it did two weeks ago."
She will argue that more has to be done to articulate and understand the benefits of immigration, while addressing concerns that those benefits are currently outweighed by tensions and divisions.
"Integration and cohesion are not states but processes. They need to be worked at, built on and nurtured," Ms Kelly will say. "Today's contexts arguably pose some of the most complex questions we have faced as a nation. We must bring a renewed impetus to these challenges."
Ms Kelly will call for "a new honest debate about integration and cohesion in the UK". She will add: "Alongside the debate we need action nationally but just as importantly in local communities themselves to build united communities and root out all forms of extremism."
Yesterday extracts of a new book by George Alagiah, the Sri Lankan-born BBC newsreader, were published in the Daily Mail, warning that "institutional tolerance for diversity" may have "led to institutional indifference to separation".
He argues that in towns such as Bradford and Halifax "multiculturalism was the perfect excuse for those who wanted to ring-fence their communities".
The debate will be revisited today when the government publishes the annual immigration statistics.
Ms Kelly will argue that her newly formed department demonstrates the government's commitment to improving community relations. "There is more that holds us together than pulls us apart," she will say, before repeating her view that there is a "battle for hearts and minds" that needs concerted action at all levels from the government downwards.
She will say the majority of the recommendations in last year's Preventing Extremism Together report, are "in hand", despite complaints from Muslim leaders that implementation has been slow.
Today Phil Woolas, her minister of state, will go to Bolton in the first of a series of government visits to nine towns and cities with cohesion concerns.
Darra Singh, the chief executive of Ealing borough council in west London, has been appointed chair of the 13-strong commission, which will hold its first meetings in September but is expected to disband once it has completed a report next year.
Under its terms of reference, the commission has been asked to look at "issues that raise tensions between different groups in different areas, and that lead to segregation and conflict" and suggest "how local community and political leadership can push further against perceived barriers to cohesion and integration".