A fight broke out between a British National Party parliamentary candidate and some Asian men as party members were out campaigning in east London.
Some men earlier swore at leader Nick Griffin and threw fruit at him and he was taken away from the scene.
The candidate for Romford, Bob Bailey, was filmed shouting out to men in Ripple Road when one of them swore and spat at him and Mr Bailey punched him.
Police were called after 1500 BST to the fight between the two groups.
'Campaign of hatred'
At the time Metropolitan Police said they were called to the incident but no-one had been arrested at the scene.
Later however, police said an 18-year-old man attended Barking police station and alleged common assault against another man.
The Barking Community Safety Unit is to look into the matter.
When asked about the fight Mr Griffin told BBC London the fight was the result of a "campaign of hatred and dehumanisation against any group of people, in this case us".
He said: "I think people have to realise that the people have spoken, this is a democratic vote and everyone has to go along with that, whether its us, our opponents or people on the streets, and if there are a few crazies or thugs on the streets I'm sure the police will deal with them quite quickly.
"The more people in the media talk this up as an issue, the more silly kids on the streets will be inclined to take the law into their hands."