There is an article on the BNP website, attempting to answer the question is the BNP racist  and justify the British National Party's position.
You can find the article here  (*)
The British National Party Argument
It is a curious article, because it does not attempt to show that the BNP is NOT racist. Rather the argument is that organisations concerned with one community or race - and the British National Party piece lists fully 32 of them - must themselves be the placed in the same category as the BNP, and are therefore racist for anyone who wishes to describe the BNP as such.
But aren't these people racist too ?
The list runs the whole gamut from the National Black Police Association and Sunny Hundal 's Asians in Media  website, to the Board Of Deputies of British Jews  and the Jewish Telegraph. a newspaper with a Jewish readership (Jewish Telegraph ), to the Action Group for Irish Youth ). That is, if the BNP is racist  then so is the Jewish Telegraph; and if the Jewish Telegraph is not racist, then neither is the BNP.
Unfortunately for the BNP, the Jewish Telegraph does not argue that the rights of non-Jews should be restricted; the Black Police Association does not seek to further the advantages of "Black" officers by preventing "White" officers from joining the police force; and the Asians in Media or Red Hot Curry websites are information services with particular audiences.
So these organisations *are* in a different category from the BNP, and the comparison is a smokescreen.
The BNP Constitution and Basic Principles
Moving on to the document which defines the BNP, in Section 2 of the "Constitution of the British National Party ", the BNP:
1 - Bars from membership people who are not of an "Indigenous Caucasian" racial background.
2 - Published a weird definition of what "Indigenous Caucasian" that means, based on people from various "Ethnic Folk Groups" being allowed to be members of the BNP. Examples are "The Anglo-Saxon-Norse Folk Community" and "The Anglo-Saxon-Indigenous European Folk Community". These are not defined anywhere, and the BNP has supplied no measurable or scientific definition of these "groups", or any basis for claiming that there is any validity behind the claim.
3 - Claims to rely in Law for those definitions on a Race Relations Act case from 1983 in the House of Lords that resulted in a school being told that they couldn't exclude a Sikh Boy from their school because his traditional long hair and turban would "accentuate religious and social distinctions in the school". The text of the case is on the Human and Constitutional website of Columbia Law School . This is the relevant segment from the BNP Constitution:
Membership of the BNP is strictly defined within the terms of, and our members also self define themselves within, the legal ambit of a defined "racial group" this being "Indigenous Caucasian" and defined "ethnic groups" emanating from that Race as specified in law in the House of Lords case of Mandla V Dowell Lee (1983) 1 ALL ER 1062, HL.
Further, the British National Party states that:
The BNP unashamedly addresses itself to the issues and concerns of the indigenous British population, and because it seeks to ensure that British people remain the majority population in this country. Opponents point to the fact that the BNP has an all-white membership, and that we address issues concerning white people.
So is the BNP racist?
The BNP claims that it is defending the interests of "white" people, and concerns itself with the interests of the "indigenous" population, while its own definitions which form the platform for that policy are (being generous) incoherent at best. It does not explain how it can implement such a distinction without a rational basis. Yet it maintains a ban on "non-white" people from membership.
The fact that the groups identified in the graphic above are all black or Asian is another tell-tale of the underlying BNP philosophy.
So, is the BNP a racist party  ? It seems to me to be an open and shut case - yes.
(*) If you link to the article I mention, I recommend linking to it using http://www.bit.ly/bnpracism/ , which does not give the site any promotion in Google.