Steve Bettley, of Merseyside Police, is among more than 12,000 supposed BNP supporters whose details have been published on the internet.

The list, initially posted on an online blog, also includes ex-policemen, a prison officer, current and former Servicemen, religious ministers, teachers and solicitors.

Police officers are banned from joining or promoting the BNP and last night Merseyside Police confirmed it was investigating whether Pc Bettley has links with the party.

A spokesman said: "We understand that the British National Party names a Steve Bettley for an alleged association with the party. Whether Merseyside Pc Steve Bettley was, or is, a member of the BNP is subject to an ongoing inquiry.

"Chief Constable Bernard Hogan-Howe has reiterated our position that membership of the British National Party is totally incompatible with the duties and values of Merseyside Police.

"We will not accept a police officer or police staff being a member of BNP."

In a statement the Merseyside Black Police Association (MBPA) appealed for "calm" while the force's inquiries are carried out, adding: "MBPA also supports Merseyside Police to ensure the safety and security of those who it feels may be at risk as a result of being associated with the BNP as a result of the publication of personal details on to the internet.

"We condemn any and all unlawful acts and will assist Merseyside Police to hold those to account who perpetrate such behaviour."

Prison officers are prohibited from joining Right-wing groups including the BNP, Combat 18 and the National Front.

A Prison Service spokesman said: "The Prison Service is very clear on this issue – we take allegations of racism very seriously and have a zero tolerance policy of those who hold racist views.

"We have dismissed a number of staff for their actions in the past, and were the first public sector employer to ban staff from being members of racist organisations.

"If we receive information indicating that a Prison Service employee is a member of a proscribed organisation, these claims would be investigated and the appropriate action taken."

The list of alleged supporters includes freelance broadcaster Rod Lucas, who was employed casually by radio station Talksport.

A spokesman for the station said: "Rod Lucas has told Talksport that as a freelance journalist he and three colleagues joined the BNP while researching a story.

"As well as joining the BNP, Rod also joined 22 other organisations including the Animal Liberation Front, the Communist Party, the anti-vivisection movement, PDSA, Save the Panda amongst others.

"Rod Lucas would like to make it clear that he does not and has never supported the British National Party."

The list has been removed from the blog where it was originally posted, but it remains available on other websites.

It suggests Yorkshire is a BNP stronghold, with 858 supporters in West Yorkshire and more than 1,600 members across the region as a whole. More than 240 people on the list live in Leeds and 109 are in Bradford – the scene of violent race riots in 2001.

BNP members first blamed former party staff for the list's publication, but yesterday took the line that it was a plot hatched by Labour supporters.

Leader Nick Griffin pledged to take court action against those behind the leak, but he welcomed the wave of publicity it has generated.

In April the BNP brought an injunction at the High Court in Manchester against five people to stop them publishing a list of members. The court ordered them to destroy all records of the information that they held.