Prominent members of the British National party are today revealed as Nazi-sympathisers and racists with abhorrent views on such diverse issues as teenage violence, David Beckham and even David Cameron's deceased son, Ivan.

The revelations undermine the party's attempts to paint itself in a more moderate light before the local and European elections and threaten to derail the electoral ambitions of its leader, Nick Griffin, who is standing as a prospective MEP.

At a time when BNP activists are claiming a surge in support in the polls, a reflection, they say, of mounting public outrage over MPs' expenses, the party has been keen to portray itself as a viable alternative to mainstream political parties.

The BNP website boasts that money is flooding into its campaign headquarters. Its administration consultant, Jim Dowson, claims the party's call centre alone received just under 12,000 calls in the first 15 minutes following the BNP's first national television broadcast. And in emails to supporters - or "patriots" as the BNP calls them - Griffin claims almost £400,000 has been stumped up by supporters to help fund the party's European election campaign.

It claims the apparent groundswell in support is down to the "British public waking from the long, deep sleep". Much of the BNP's recent success has been down to its ability to shake off the patina of far-right extremism that has alienated most voters since its inception. But this month the veneer slipped when it emerged that a Salford-based BNP candidate in the European elections had set his Facebook status to read "Wogs go home". Eddy O'Sullivan, 49, wrote: "They are nice people - oh yeah - but can they not be nice people in the fucking Congo or... bongo land or whatever?" O'Sullivan, who also joined an internet group called "Fuck Islam", denied that the comments were racist and insisted they were made in private conversations between individuals. "I also may have had a drink at the time," he added.

Amid the furore, the BNP's leaders promised an investigation into O'Sullivan's comments. The party's officials also circulated urgent emails urging its members that "particular care should be taken when making comments on chat forums and other sites such as Facebook. Do not make the mistake of thinking that comments posted on these sites are secret or hidden. Making inappropriate comments on these sites will be regarded as a very serious disciplinary offence. Please ensure that this message is passed quickly to all members in your area and that it is acted upon. We are entering a very critical time in our party's history and cannot afford careless and stupid talk that can undermine the hard work of our activists."

But the anti-fascist organisation Searchlight has spent months infiltrating the far right's network of websites and chatrooms and found that many BNP activists share O'Sullivan's views.

They include:

• Jeffrey Marshall, senior organiser for the BNP's London European election campaign. Following the death of David Cameron's disabled son Ivan, Marshall claimed in an internet forum discussion: "We live in a country today which is unhealthily dominated by an excess of sentimentality towards the weak and unproductive. No good will come of it."

Later, in response to comments made by others on the site, Marshall is alleged to have written: "There is not a great deal of point in keeping these people alive after all." He said the comments were private and some had been paraphrased and taken out of context. He admitted making the former comment, but said he could not recall making the latter one in an email to the forum, a copy of which is in the Observer's possession.

• Garry Aronsson, Griffin's running mate for the European parliament in the North West, posts an avatar on his personal web page featuring a Nazi SS death's head alongside the statement, "Speak English Or Die!" Aronsson proclaims on the site: "Every time you change your way of life to make immigrants more comfortable you betray OUR future!" He lists his hobbies as "devising slow and terrible ways of paying back the Guardian-reading cunts who have betrayed the British people into poverty and slavery. I AM NOT JOKING."

• Barry Bennett, MEP candidate for the South West, posted several years ago under a pseudonym in a white supremacist forum the bizarre statement that "David Beckham is not white, he's a black man." Bennett, who is half-Jewish according to the BNP's deputy leader, Simon Darby, continued: "Beckham is an insult to Britishness, and I'm glad he's not here." He added: "I know perfectly respectable half-Jews in the BNP... even Hitler had honorary Aryans who were of Jewish descent... so whatever's good enough for Hitler's good enough for me. God rest his soul."

• Russ Green, MEP candidate for the West Midlands, posted recently on Darby's web page: "If we allowed Indians, Africans, etc to join [the BNP], we would become the 'British multi-National party' ... and I really do hope that never happens!" Darby said he echoed Green's sentiments.

• Dave Strickson, a BNP organiser who helps run its eastern region European election campaign, carried on his personal "Thurrock Patriots" blog a recent report of the fatal stabbing of a teenager in east London beneath the words "Another teen stabbed in Coon Town". The site also carried a mock-up racist version of the US dollar entitled "Obama Wog Dollar". Darby said the BNP did not endorse these comments and described them as "beyond the pale".

When confronted in the past about the extreme views of some of its members, the BNP senior hierarchy has often tried to dismiss them as unrepresentative of the party's core membership. But it appears that they run right to the top of the party.

Lee Barnes, the BNP's senior legal officer and one of Griffin's closest allies, has posted a video on his personal blog of a black suspect being beaten by police officers in the US and describes it as "brilliant". Barnes adds: "The beating of Rodney King still makes me laugh."

Barnes told the Observer his comments were "nothing to do with colour" but were merely a reflection of his belief that the police should have more powers to punish perpetrators of crime by "giving them a good thrashing".

But anti-fascist groups said such comments portrayed the BNP in its true light. "This is the face of the modern BNP," said a spokesman for Searchlight. "The comments of Nick Griffin's candidates and officials are sickening beyond belief. They have tried to hide their agenda of racism and hate from the voters, and they have failed."

Separately, concerns exist about the historic links between the BNP and extremist groups. Gary Pudsey, a BNP organiser running the Yorkshire and Humber campaign, was once a regular at National Front meetings. A young Pudsey was also photographed with the late Max Waegg, a Nazi second world war pilot who wrote articles for the white supremacist magazine Spearhead

Martin Page is a BNP treasurer and his wife Kim is a senior fundraiser for the party. Both have been photographed alongside Benny Bullman, the lead singer of Whitelaw, the white supremacist band whose songs include Fetch the Noose, We're Coming for You and For White Pride.

And Dowson, the BNP's senior administrator, who appears on the party's website talking about the success of its call centre's fundraising activities, has also been dogged by allegations that he has enjoyed close relationships with hardline loyalist groups in the past. The 45-year-old has also been the public face of the LifeLeague, the militant anti-abortion group that has hijacked Britain's pro-life debate. He has regularly appeared on television to pronounce terminations a sin and has published the names of abortion clinic staff, placing many in fear for their personal safety.

That the BNP has become a magnet for extreme-right sympathisers is understandable given Griffin's own background. The Cambridge graduate was himself a member of the NF before going on to form the International Third Position, a neo-fascist organisation with links to the Italian far right.

But aware of the party's need to raise funds from middle England, Griffin has repeatedly attempted to portray his party as the "reasonable" face of patriotism in its bid to broaden its appeal. The approach has paid dividends, with the party having gained 55 seats on local councils, including a seat on the Greater London Authority. This June it is contesting every UK seat at the European elections and there have been predictions it could win overall control of Stoke City Council.

Darby, Griffin's deputy and the BNP's spokesman, accused Searchlight of "distorting the BNP's message" in a bid to derail its political ambitions. He accused the organisation of being "merely a front for the Labour party, paid for by National Lottery funds". Darby said: "When you put it in the context of what's been happening at Westminster, a few scribblings on Facebook hardly seems something to get worried about."