In December 2006, it was revealed that a The Guardian journalist, Ian Cobain, had worked undercover in the BNP for seven months, becoming the party's central London organiser.[68][69] Among the accusations made by the paper was that the BNP used "techniques of secrecy and deception ... in its attempt to conceal its activities and intentions from the public". It asserted that the BNP operated with a "network of false identities" and organised rendezvous points to allow members to be directed to "clandestine meetings". Party members were directed to avoid "any racist or anti-semitic language in public". Cobain also claimed that the membership in central London had expanded beyond the party's traditional range, now including "dozens of company directors, computing entrepreneurs, bankers and estate agents, and a handful of teachers".[68]

Following the report, the campaign group Unite Against Fascism called for ballerina Simone Clarke to be dismissed from the English National Ballet, because her views on immigration were "incompatible with a leading arts institution such as the English National Ballet" and because she had "used her position to support a party which fosters division".[70] Clarke said: "the BNP is the only party to take a stand against immigration".[70]

The BNP was investigated by the Electoral Commission in 2007, after The Guardian revealed that it had set up a front organisation to raise money from sympathisers in the United States.

"....The EDL leadership has estimated that the EDL has 100,000 members.[31] A research group has given a lower figure of 25,000 to 35,000 members.[32]...."