BNP leader Nick Griffin said the party had lodged a complaint with police
Merseyside Police is continuing to investigate whether one of its constables has any links to the British National Party (BNP).
Pc Steve Bettley was listed in a leaked membership document published online.
Police officers have been banned from being members of the anti-immigration party since 2004.
"Whether Merseyside Pc Steve Bettley was, or is, a member of BNP is subject to an ongoing inquiry," said a force spokesman.
The document, which dates from 2007, has the names, addresses, jobs and phone numbers of 12,000 people named as members. It was published on a blog.
Officers are banned from joining or promoting the BNP because it would damage race relations, according to the Association of Chief Police Officers (ACPO).
A Merseyside Police spokesman said: "We understand that the BNP names a Steve Bettley for an alleged association with the party.
"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."
The Independent Police Complaints Commission (IPCC) received a voluntary referral on Wednesday from Merseyside Police but will not be involved in the inquiry.
Naseem Malik, IPCC Commissioner for the North West, said: "I have every confidence that Merseyside Police will investigate this matter thoroughly."
Earlier this year, the BNP obtained an injunction at the High Court in Manchester banning any publication of the list.
Party leader Nick Griffin said the list was "essentially genuine", but a number of names of people who were not or are not party members had been added.