Right-wing groups who claim to oppose Islamic extremism are trying to provoke violence on Britain's streets, the communities minister has said.
John Denham spoke after clashes between different groups at a new London mosque, during a march by the group Stop the Islamification of Europe.
Demonstrations by an affiliated group, the English Defence League, have led to violence in Birmingham in recent weeks.
Mr Denham said protests could get "out of control" unless action was taken.
Ten people were arrested on Friday after scuffles broke out at the site of a new five-storey mosque planned next to the Harrow Central Mosque in north-west London.
Local Muslims and members of Unite Against Fascism (UAF) confronted protesters from Stop the Islamification of Europe and chased them away.
A minority of young Muslims then turned on police, throwing bricks, bottles and firecrackers.
Violence broke out in Birmingham earlier this month and last month when members of the English and Welsh Defence Leagues, and another group called Casuals United, took to the streets.
Bricks and bottles were thrown at police
Mr Denham said such right-wing protesters were trying to provoke an "overreaction" from the Asian community.
"Then people blame the people who overreact and the situation gets out of control," he said.
"We know from the recent past that provocation can lead to community division and overreaction unless we nip it in the bud very quickly."
The minister singled out the EDL in particular: "If you look at the types of demonstrations they have organised, the language used and the targets chosen, it looks pretty clear that it's a tactic designed to provoke, to get a response and create violence.
"It's important that we, right across government, make sure this does not happen.
"We need to make sure people realise we are going to deal with this and that people recognise there is not a need to tackle this through counter confrontation."
Mr Denham said the EDL's tactics were similar to those employed by the British Union of Fascists in the 1930s, but stressed that they did not present anything like the same "potency, organisation or threat".
But local Labour MP and former Home Office minister Tony McNulty has criticised that comparison as too simplistic. "It affords this rag-bag motley crew a status they simply don't deserve," he said.
"This was a house of God they were objecting to. They can wrap it up in whatever politics they like, but they were anti Muslim religion."
The EDL has further demonstrations planned for Manchester, Leeds and Luton over the next few weeks.
They are also expected to draw hundreds of supporters to a demonstration in Trafalgar Square on Sunday.
Jobs and homes
The Department of Communities said Mr Denham's comments were the start of concerted efforts to undercut the growth of far-right extremism, particularly within predominantly white working class communities.
About 1,000 people turned up for the demonstration
A campaign will begin "during the autumn" to address the sense of alienation and disaffection some people are feeling, a spokesman said.
It will include intensive engagement at neighbourhood level and greater effort to understand why some people currently feel overlooked or that system is weighted against them.
For example, the department says, there will be more effort to make sure money for job schemes and social homes are going to the right places and local residents feel fully involved in how government funding is spent.
The EDL's website says the group exists to oppose Islamic extremism, but it is not against individual Muslims.
Anti-racist campaigners say the League has links with the far-right and with football hooliganism.
Unite Against Fascism says that the EDL is "a racist group, out to attack Asians".
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.