The BBC recorded an officer dressed in a Ku Klux Klan hood

David Blunkett told the BBC he does not have direct power but called on chief constables to come up with a plan.

He said the diversity test taken by new recruits would make it "untenable" for trainees to be BNP members.

And he would like the police to copy the prison service, where staff involved with the BNP can be sacked.

Racism test

Speaking on the BBC Radio 4's Today programme, Mr Blunkett said: "It's an area where I can only exercise influence rather than direct power.

"I do not believe it's tenable for a member of the British National Party to be a police officer in this country.

"I don't believe they could pass the diversity assessment that's being put in place."

Fifteen forces in England and Wales have diversity tests which are to be rolled out to all forces next year.

Trainees are tested in role play situations on their sensitivities to race issues and can be failed if they demonstrate a deep-seated prejudice.

I do not have the legislative power to order them, in operation terms, who they should and should not take, but I will use the influence I have David Blunkett Home Secretary

For current officers, Mr Blunkett is wary that he does not want the force to appear to heavy-handed.

And nothing can be done about those that may vote BNP and keep it to themselves.

He said: "I think it's beholden on chief constables to work with us in finding a way we don't witch-hunt people. Looking at people on holiday is not what we're addressing.

"What we are addressing is deep-seated racism and being a member of the BNP is an indication, not only of their views, but their willingness to participate in a racist party."

A BNP councillor recently said there were between six and 12 party members serving with West Midlands Police.

Simon Darby, a BNP representative on Dudley Metropolitan Borough Council, also said that a former force inspector was on a shortlist to run as a candidate in next year's European elections.

Any legislation on the issue would face a legal challenge, but Mr Blunkett said the Prison Service had adopted a strict practice on racism which should be copied for the police.

Within the Prison Service, staff are told that they are not allowed to belong to "groups and organisations with racist philosophy, aims, principles or policies".

The Commission for Racial Equality is to launch a formal inquiry into all police forces in England and Wales, following a BBC documentary which exposed racism at a police training college in Cheshire.