A scuffle erupted on the streets of Croydon today as the British National Party presented some of its candidates for the forthcoming local and Westminster elections.
One anti-fascist protester broke through a police cordon and tried to punch a BNP member before being tackled to the ground and taken away by police officers.
The BNP was presenting its candidates outside the headquarters of the UK Border Agency, in south London.
Anti-fascist protesters were waiting for the BNP outside Lunar House where the event was taking place.
They shouted "Nazi scum. Off our streets" and "Smash the BNP".
BNP London organiser Robert Bailey, who is standing as a parliamentary candidate in Romford, Essex, had earlier told a group of around 40 BNP candidates that they were there to put immigration on the election agenda.
He said: "The leaders of the main political parties will be holding a meeting tonight at the TV studios to discuss the future of Britain.
"Up until this moment, nobody has mentioned immigration. The reason why the British National Party is here today is to draw the public's attention and the world's attention to the immigration crisis that is facing ordinary British citizens."
Mr Bailey, who is also a local councillor in Barking and Dagenham, said immigration was the second-biggest issue after the war in Afghanistan for politicians and the Government to face up to.
"We are here today to break the silence," he said.
The BNP plans to field around 350 parliamentary candidates for the forthcoming General Election on May 6.
After the scuffle, Mr Bailey said that the BNP had the right to protest and anti-fascist campaigners had a right to counter-protest.
He said: "Unfortunately some of them have decided to cause a scene."
Party leader Nick Griffin was not present at today's gathering.
Asked where Mr Griffin was, Mr Bailey replied: "You will have to ask him."
The BNP candidates held aloft banners reading "Britain is full up" and "Asylum seekers: Don't unpack, you're going back".
Andrew Pelling, the former independent MP for Croydon South who is standing for re-election, joined the anti-fascist protest organised by Croydon Trades Council, the Public and Commercial Services (PCS) Union and Unite Against Fascism.
Mr Pelling said he had written to Home Secretary Alan Johnson to complain that the BNP had been allowed to gather outside a building used to process asylum and immigration claims.
"It's important that they should be allowed to demonstrate but I think discretion should have been employed and the protest taken place elsewhere," Mr Pelling said.
"They are trying to create flashpoints. These protests are pretty inflammatory when they take place outside Lunar House - we're trying to show that we are a society of tolerance and compassion."
Mark Serwotka, general secretary of the PCS union, also spoke out over the decision to allow the BNP to protest outside the building.
"It's a scandal they can demonstrate on Government property," he said.
"Asylum seekers and immigrants come here to have their cases processed, and it's sickening that they should be faced with the BNP.
"People are being given police escorts in and out of the building - that can't be right.
"A lot of PCS members work in the building, and I don't believe people should have to go through that to get to work either."
Mr Serwotka said the person who had been taken away by the police after attacking the BNP gathering was nothing to do with the official anti-fascist demonstration, but added: "It doesn't surprise me, given the hatred the BNP spout, that some people take matters into their own hands."
Mr Bailey had earlier asked why the PCS workers were outside the building, saying: "Get back to work."
He also said the party was standing in an "unprecedented" number of constituencies, adding: "The BNP is going from strength to strength because the ordinary working people are fed up with being pushed to the back of the queue."
Current immigration levels meant services in many parts of the country were "at breaking point", Mr Bailey, 44, said.
"It is creating so many problems in this country. We cannot afford to continue taking immigrants from the EU and other parts of the world - it's plain economics."
Compared to the highly-organised manifesto launches of other parties in recent days, the BNP gathering got off to an unusual start.
Candidates and journalists amassed outside East Croydon railway station, awaiting further details on where the meeting would take place.
Along with a handful of police officers, party officials eventually led the group away from the station and on a roundabout route through the streets of Croydon to the back of Lunar House.
It meant coming face-to-face with the anti-fascist protesters who were already in position - with the BNP group using the stairways of an underpass to avoid coming too close.
Police then directed the candidates into an area cordoned off by metal barriers, before banners were unfurled and placards held aloft.
As the anti-fascist demonstrators chanted anti-BNP slogans, the group responded with a call of "Commie scum, off our streets".
Hecklers challenged the BNP on their education policies as Mr Bailey addressed the candidates, while several figures dressed from head-to-toe in black and with their faces covered lined up close to the metal barriers.
Police officers faced them in a line, but they charged forward and one man was able to break the cordon and attempted to land a punch before being wrestled to the ground.
He was then handcuffed and taken away, while his colleagues continued to chant anti-fascist slogans towards the BNP meeting.
As the commotion eventually died down, one BNP candidate said: "See, we're a peace-loving party. Full of pensioners."
The BNP manifesto was never presented, and is expected to be officially unveiled later this month.