People who are seeking to come to the UK to work or to join a spouse already living here should be required to learn English, an expert body says.
The commission says poor English skills hinder integration
The Commission on Integration and Cohesion says language is the single largest barrier to community relations.
Communities Secretary Ruth Kelly launched its report, saying far-right groups which spread "myths" about the multi-racial UK must also be tackled.
Critics say the English language proposals are "impractical".
Ms Kelly set up the commission last summer amid pressure over multiculturalism and claims that not enough had been done to tackle issues raised by the July 2005 London bombings.
The commission was asked to come up with policies to help make an increasingly diverse society more cohesive.
In its interim report, the commission asks whether enough is being done to ensure that the correct first steps are taken to integrate two key groups into British society: foreign migrant workers and spouses.
If people do not speak any English on coming to the UK, the commission says ministers should consider changing immigration rules to ensure they have some command of the language before being allowed to come as a worker or through marriage.
Commission chairman Darra Singh said: "Learning English is clearly the responsibility of the individual, but local authorities, central government and employers have a key role in supporting migrants to improve their language skills."
He added: "If you can't speak English - whether you are a new migrant or someone who has lived here for years - you are on a path to isolation and separation."
Speaking at the London launch of the interim report, Ms Kelly said helping migrants to integrate must be accompanied by improved efforts to take on "poisonous" far-right groups.
She accused such groups of promoting division by spreading "myths and misconceptions" about Britain's multi-racial society.
"And it is because of this that I am determined to achieve a step change in the Government's work to tackle far-right extremists," she added.
She said policies over past decades had sometimes "emphasised what divides us at the cost of what unites us".
Under current proposals, only migrants who are unemployed or on benefits will qualify for free English lessons from September.
The government also proposes to cut benefits to those who cannot prove they are learning English.
Rehna Azim, a barrister and editor, said suggestions that immigrants should learn English before arriving in Britain were "impractical".
She told the BBC's Today programme: "The idea that some young woman in Pakistan or Bangladesh can go to a class in her village to learn English when she knows nothing about this country is really... impractical and it is not going to happen."
She said what was needed was an integration programme showing arrivals in the UK around their new cities and introducing them to available services.
Learning English would then become a practical necessity, she said.
Birmingham Labour MP Khalid Mahmood told BBC Five Live that it was not the problems of those who could not speak English but the issues facing young radical Muslims and alienated youths who already speak the language that needed to be tackled.
Nick Pearce, director of the Institute for Public Policy Research, said the government needed to put more resources into language training.
He added: "The more people living in Britain who speak English, the better.
"But it would be impractical and unrealistic to expect the families of short-term migrant workers coming to do key jobs in our economy to pass a test before they arrive."
Ms Kelly said her department would study the commission's recommendations carefully in June before responding.