The British National party's already troubled election campaign descended into violence tonight when one of its councillors was caught on camera getting into a fight with a group of Asian youths.

Bob Bailey was canvassing with other BNP members in the party's key target seat of Barking, in east London, when they became involved in an argument with a group of teenagers. Footage appeared to show one of the teenagers spitting at the BNP activists, before the youth is apparently punched to the ground and kicked in the body.

Police said they were called to investigate reports of a fight at 3.10pm today, but were taking no further action. The BNP refused to comment on the incident.

Earlier in the day, eyewitnesses said Nick Griffin, the BNP leader, had been pelted with tomatoes by several white youths as he campaigned in the area.

"It was a couple of white lads, and they just picked up a couple of tomatoes and threw them at Griffin," said a shopkeeeper who witnessed the incident. "This is why we really don't want the BNP round here. Everyone gets on well, but they are just trying to stir up trouble and divide people."

The shopkeeper, who did not want to be named, said Griffin ran into his car and was driven away. "It was then that a couple of lads on bikes followed his car to see what was going on. I think that was when they caught up with some more BNP members. There was an argument and they were pretty viciously attacked."

The violence was the latest setback for the BNP campaign. Yesterday the BNP's website was closed down and replaced with a posting from Simon Bennett, the party's website manager, stating he had been "in dispute with some elements of the management of the party" and claiming there had been "several attempts to steal" his work. The website was later reinstated, but on his own blog Bennett added that there had been a number of "highly questionable shenanigans going on at BNP HQ" with which he was unhappy.

Meanwhile, a BNP leaflet designed to woo the black Christian vote in Barking and Dagenham has been branded "obscene" by one of its recipients.

The targeted leaflet, which accuses Labour of undermining Christian values and promoting "ungodly lifestyles", was sent to 24,000 people in the borough.

It features a picture of Nick Griffin next to the Rev George Hargreaves, the leader of the Christian party, and was sent out last week after the BNP trawled the electoral register looking for people with "African names".

In it, Griffin says: "I am writing to you personally to set your mind at rest. A lot of rubbish is being written and talked about how the BNP is supposed to be some kind of 'threat' to black and ethnic minority groups in Barking … I want to reassure you that, as a Christian and a man who believes passionately in core British values including democracy and freedom, I am not standing in this election to persecute or hurt anybody, or any race and religion."

After berating the government for damaging Christian values and encouraging "the spread of Islam", he adds: "Surely, no believer can vote Labour and walk with the Lord Jesus Christ.

A BNP spokesman said: "Our campaigners trawled through the electoral register and identified 24,000 African names. They have each received a personal letter from Nick Griffin to counteract the alarmist claims being made by [Labour MP] Margaret Hodge that if the British National party are elected the borough will descend into chaos."

Hargreaves told the Guardian there was nothing his party could do about his image appearing on the leaflet.

"I haven't seen the leaflet, so I can't comment on it, but we're taking legal advice," he said. "[But] they haven't defamed us, so there's nothing we can do."

He said that although there was a "politics of fear stalking Barking", the Christian party was urging people to vote on principles rather than prejudice.

"Our message is faith, not fear," he said. "Our scriptures tell us that we should not go to the polls because we are frightened of anybody, but because we believe in the values of those people who are standing."

One Barking and Dagenham resident – a British citizen with Indian Caribbean heritage – described the BNP leaflet campaign as "obscene".

The resident, who did not want to be identified, does not have an African first or second name and expressed surprise at receiving the leaflet.

"I was extremely concerned to receive direct mail from the BNP, particularly as it was sent to me on the basis of my ethnicity," said the resident.

"I find it disturbing that a political party with far-right links and extreme views is keeping lists of people categorised by ethnicity. Ethnic profiling is not an acceptable means of polling and I am very scared."

The leaflet, the resident added, had stirred fears that the BNP would "consider repatriation of me and my mixed-heritage child to several countries that I no longer have links to … It is obscene."

The BNP did not respond to the Guardian's questions about how it had obtained data on Barking and Dagenham residents who do not have African names.

Although the party had predicted it would create a "political earthquake", claiming it was on course to win two parliamentary seats and take control of Barking and Dagenham council, its campaign has been beset by problems, and it is floundering in the polls.

Internal criticism over Nick Griffin's leadership came to a head last month when the publicity director, Mark Collett, was arrested on suspicion of threatening to kill him. In Stoke, the party's number two electoral target, Alby Walker, who led the BNP on the local council for four years, is standing as an independent.

• Read the BNP letter