Dozens of people were arrested in London on Saturday when rival groups faced off over the killing of a British soldier by suspected Islamists.
The Metropolitan Police said 58 people from the Unite Against Fascism group were arrested after they gathered to oppose a rally by the British National Party near Parliament.
Two men are now charged over the slaying of Drummer Lee Rigby, 25, near the Woolwich Barracks on 22 May. In total, 12 people have been arrested.
The BNP had hoped to march in Woolwich but were banned from doing so by the police, fearing public disorder.
Many protesters carried the British flag and some had signs saying "Hate preachers out".
"Britain is a tinderbox waiting to explode," BNP leader Nick Griffin told AFP.
"We are here - I hope - starting a debate to point out the only way out, or the best way to get peace, is to disengage so there's a peace treaty between the West and Islam.
"We leave their lands - we stop attacking them, we stop bombing their wedding parties - and in turn, they leave ours. Then we can have peace."
UAF demonstrators held banners reading "Say no to Islamophobia".
"They're trying to take advantage of the very sad murder of a young soldier," UAF chair Steve Hart told AFP.
"We don't allow the BNP on the streets without opposition.''