The Labour MP, who chairs a group of politicians who are opposed to Brexit, warns in a report that anti-immigrant rhetoric is making it harder for new arrivals.
Mr Umunna said: “The demonisation of immigrants, exacerbated by the poisonous tone of the debate during the EU referendum campaign and after, shames us all and is a huge obstacle to creating a socially integrated nation.
“We must act now to safeguard our diverse communities from the pedlars of hatred and division while addressing valid concerns about the impact of immigration on public services, some of which can contribute to local tensions.
“We must start by valuing the contribution of all ethnic and minority communities to the UK. Rather than being seen as security risks, immigrants should be viewed as Britons-in-waiting, keen to participate in their community.
“The best way to do this isn’t to leave newcomers and their communities to sink or swim, but to offer migrants more support to integrate into our society.”
Migrants should be treated as Britons-in-waiting who are expected to eventually gain citizenship instead of being viewed as security threats, the All Party Parliamentary Group (APPG) on Social Integration said.
It found newcomers are increasingly leading parallel lives and warned that anti-immigrant rhetoric is making it harder for people to become fully involved in British life.
Critics have accused the group of trying to keep EU freedom of movement through the back door.
Richard Tice, co-chairman of pro-Brexit campaign Leave Means Leave, said: “This is typical of Chuka Umunna – a member of the metropolitan liberal elite who is completely oblivious to the concerns of millions of hard-working British families across the country.
“There is nothing ‘poisonous’ about wanting to take back control over Britain’s borders, in fact he should be ashamed to suggest there is.”
He claimed Mr Umunna was “in complete denial about the referendum result and is trying to retain a form of freedom of movement which is completely against the democratic will of the British people”.
It follows an awkward interview with BBC host John Humphrys who attacked the Labour MP over his party’s lack of clarity over Brexit saying the party was “ducking” questions on the issue.
Mr Humphrys said the public was still unclear about the party’s position on whether the UK should stay within the customs union and single market.
Speaking on the Today Programme on BBC Radio 4, Mr Umunna said he would be arguing for staying in both European Union entities.
But Mr Humphrys highlighted this was different to Labour leader Jeremy Corbyn’s position.
Mr Humphrys said: “What I’m not clear about, still, is what your party’s position on membership of the customs union and single market after Brexit is going to be.
“With the greatest respect, your opinion matters, obviously, which is why I’m asking you, but I’m asking you really for your party’s position as opposed to what you would like to happen.
“I suspect there may be a slight difference here.”
The shadow business secretary from 2011 to 2015 replied the country “absolutely” needed to argue for the UK to remain in the single market and customs union.
August 25th, 2017: Express