Simply because information is publicly available online, does not make it lawful to use any personal data involved, said Paula Barrett, partner in the IT group at Eversheds.
"Care must be taken by employers and other third-parties seeking to make use of such details to ensure that such processing does not inadvertently place them in breach of data protection legislation," she said.
Data protection rights are not conditional upon beliefs of the individual involved and the publication of personal data creates potential criminal and civil liabilities for anyone involved, said Barrett.
"Even where membership of a lawful political party causes concern, particularly in a democracy, those party members have the same rights as members of any other political party to have their personal data protected," added Barrett.
BNP members have expressed concerns about potential backlashes and job losses after being exposed as members of the far-right party.
It is illegal for armed forces personnel and police officers to be members of a political party and other are in roles where membership of the BNP may be frowned upon.
Barret said employers considering dismissal or disciplinary action as a result of these details must also ensure they comply with employment laws otherwise they may face action for unfair dismissal and/or discrimination on the grounds of race or belief.