Conservatives and far-right make gains amid record low turnout in 27-nation poll.
About 400 demonstrators, brandishing placards reading “Stop the Fascist BNP” and shouting “Smash the BNP” were involved in the protests. Three people were reportedly arrested.
Speaking to Al Jazeera outside BBC Television Centre, Weyman Bennett, from Unite against Fascism, argued that Griffin should not be given a platform on the show despite arguments on the grounds of free speech.
Bennett said: “The BNP is not a normal party, it’s a Nazi party, it doesn’t accept the other democratic principles that everybody has been created equally.
“They are a party which is dedicated to bringing race hate, they celebrate attacks and murders on people they consider to be inferior.
“Nick Griffin denies six million people were murdered in the gas chambers.
“The BNP’s not a democratic party, it believes in well-aimed boots and fists to persuade people to divide on the basis of apartheid; why should we support that?”
Mark Thompson, director-general of the publicly funded BBC, defended the decision, saying it was based purely on support for the BNP at the ballot box in recent elections and that it was up to politicians to bar parties.
Gordon Brown, Britain’s prime minister, said the choice of panellists was a matter for the BBC, but added that he thought Griffin’s appearance would backfire on the right-wing party.
“At every point, I believe we have got a duty to expose the BNP for what are racist and sectarian politics,” Brown said.
“Anybody who listens to what they are really about will find that what they are saying is unacceptable.”
Jack Straw, the country’s justice secretary, will join the panel to debate with Griffin, reversing Labour’s previous refusal to share a platform with the extreme right.
The BNP, which calls for a halt to immigration and Britain’s withdrawal from the European Union, as well as seeking to encourage voluntary repatriation of immigrants, won two seats in European parliament elections in June.
“What it does is it sanitises them, that’s what it does, that’s why it’s wrong”
Diane Abbott, British member of parliament
It has no seats in the national parliament, but will field hundreds of candidates in a general election due by next June.
The mainstream parties fear it could siphon off voters angered by a deep recession and a scandal over politicians’ expenses.
In a letter to supporters on the BNP’s website, Griffin said his appearance on the programme would be a “milestone in the indomitable march of the British National party towards saving our country”.
Some political commentators have noted that Jean-Marie Le Pen, the leader of France’s far-right National Front, used his television debut on a similar French political show in 1984 to bolster support and recognition.
Diane Abbott, Britain’s first black woman MP, said Griffin’s appearance was “wrong and offensive”.
“What it does is it sanitises them, that’s what it does, that’s why it’s wrong,” she said.
Griffin will answer audience questions in a panel with Straw, Chris Huhne, the Liberal Democrat home affairs spokesman, Sayeeda Warsi, the Conservative community cohesion spokeswoman and Bonnie Greer, a writer from the US.