BNP leader Nick Griffin and party activist Mark Collett have been cleared of inciting racial hatred after a retrial at Leeds Crown Court.
The pair were greeted outside court with chants of "freedom"
Mr Griffin, 46, from Powys, Wales, had denied two charges of using words or behaviour intended to stir up racial hatred in a speech in Keighley.
Mr Collett, 26, of Leicestershire, was cleared of four similar charges.
Chancellor Gordon Brown has told the BBC race laws may have to be revised in light of the acquittal.
Mr Griffin and Mr Collett were charged in April 2005 after the BBC showed a secretly-filmed documentary The Secret Agent in 2004.
The party leader smiled and nodded as the foreman of the jury read out the unanimous not guilty verdict.
Outside court, Mr Griffin and Mr Collett were greeted with chants of "freedom" by about 200 supporters, some of whom waved the union flag.
A small number of anti-fascist protesters shouted as Mr Griffin addressed the crowd on a megaphone.
He said: "What has just happened shows Tony Blair and the government toadies at the BBC that they can take our taxes but they cannot take our hearts, they cannot take our tongues and they cannot take our freedom."
Mr Griffin said his co-defendant had worked "incredibly hard" for the BNP but had been living under the threat of a prison sentence since the age of 23.
Mr Collett, the party's head of the publicity, said: "This is the BNP - two, BBC - nil."
He branded the BBC "cockroaches" and added: "The BBC have abused their position.
Mr Griffin had described Islam as a "wicked, vicious faith"
"They are a politically correct, politically biased organisation which has wasted licence-fee payers' money to bring two people in a legal, democratic, peaceful party to court over speaking nothing more than the truth."
In a statement, the BBC said its job was to bring matters of public interest to general attention.
"In this case the matters raised in The Secret Agent were seen by a large section of the public and caused widespread concern," the statement read.
"The BBC has an important role in doing this.
"However, the question of whether criminal offences have been committed is of course a matter for the police, prosecuting authorities and the courts and not for the BBC."
Speaking to the BBC after the acquittal, Chancellor Gordon Brown said race laws may have to be tightened.
He said: "I think any preaching of religious or racial hatred will offend mainstream opinion in this country and I think we've got to do whatever we can to root it out from whatever quarter it comes.
"And if that means we've got to look at the laws again I think we will have to do so".
The Crown Prosecution Service said it was satisfied there had been sufficient evidence for a "realistic prospect of conviction" and it had been in the public interest to proceed.
During the trial, the jury heard extracts from a speech Mr Griffin made in the Reservoir Tavern in Keighley, on 19 January 2004, in which he described Islam as a "wicked, vicious faith" and said Muslims were turning Britain into a "multi-racial hell hole".
At the same event, Mr Collett addressed the audience by saying: "Let's show these ethnics the door in 2004."
In his closing argument, Nick Griffin's barrister said his client's words were part of a "campaign speech of an official and legitimate party".