As Nick Griffin drove towards Westminster to celebrate the British National Party's European election success he would have been hoping for a decent turnout for the press conference he had planned.

Ever the savvy media operator, the far-right leader would have known that his extremist party desperately needed to keep riding the wave of press coverage. He need not have worried. Before he could begin speaking, a group of approximately 100 demonstrators from Unite Against Fascism began pelting the BNP leader and his shaven-headed bodyguards with eggs and chanting "Nazi scum!" The story topped the news agenda for the rest of the evening.

The BNP could hardly contain its delight. As Simon Darby, the party's number two, put it in his blog yesterday: "I wonder how much the resultant publicity from today's aborted press conference would have cost?"

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For those wishing to confront the rise of a party with overtly racist policies, the latest protest against the BNP goes right to the heart of how anti-fascist campaigners should deal with an extremist organisation that roughly 900,000 Britons now regularly vote for. Should our fascists be ignored or confronted? Shouted at or spoken to?

As one veteran anti-racism campaigner put it yesterday: "Throw eggs at the BNP and you might highlight how people are outraged that an extremist party has made headway in British politics. But you also risk handing them publicity on a plate."

For organisers of Unite Against Fascism, a coalition of anti-fascist campaigners with strong trade union links formed out of the Anti-Nazi League and the National Assembly Against Racism, giving the BNP a publicity coup was a risk they were willing to take.

"Thanks to its European election wins the BNP had already been on the front page of virtually every newspaper," says Weyman Bennett, who helped organise the protest. "What we had to do was deny it respectability. The danger is that [the BNP] is trying to portray itself as a legitimate, mainstream party rather than the fascist, racist party that it actually is. If it continues to get the votes of ordinary, respectable working-class people, it will become increasingly hard to stop."

Backed by the TUC and major trade unions like Unison and T&G and with close links to the Socialist Workers Party, overt confrontation is a tried and tested formula for Unite Against Fascism. For Sabby Dalhu, head of the National Assembly Against Racism, Tuesday's protest was about stopping the BNP from celebrating its victory.

"Ultimately the BNP didn't get to call the shots and command the publicity the way it wanted to," she said. "Instead of a press conference celebrating the victory, the news was dominated by how anti-fascists had told the world that the vast majority of British people find the BNP abhorrent."

But others believe tactics like egg throwing ultimately backfire. "The protest was a failure because it enabled BNP members to portray themselves as free speech victims – it played right into their hands," said Simon Hughes, the Liberal Democrat MP for North Southwark and Bermondsey and a staunch critic of the BNP. For Ann Cryer, the veteran Labour MP for Keighley who stood against Nick Griffin in the 2005 general election, some anti-fascist groups were more of a hindrance than a help.

"At one stage of the campaign," she recalled, "I had to phone a couple of groups to ask them not to come up because I knew the kind of protests they [carry out] would only give the BNP the headlines that it craves."

Part of the problem for anti-fascist campaigners is that Unite Against Fascism and Searchlight – the two main organisations that campaign against the BNP – fundamentally disagree over how the far right should be confronted.

Activists from UAF are generally more willing to resort to direct action tactics, while members of Searchlight, which specialises in infiltrating the BNP and publishing exposés of its activities in the group's magazine, are wary of doing anything that hands the BNP extra publicity. The disagreements are so stark that Searchlight finally withdrew from the Unite Against Fascism coalition in 2005.

Dan Hodges, a spokesperson for Searchlight, believes confronting the BNP now that it has seats in Brussels will take a mutli-pronged campaign from all sectors of British society. "Ultimately we need to be tough on fascism, tough on the causes of fascism," he said. In other words, it will take more than a few broken eggs.