Last month the far-right party voted to approve changes to its constitution to allow black and Asian people to become members.
The vote followed the threat of a possible court injunction over its whites-only membership by the Equality and Human Rights Commission (EHRC).
The BNP will be back at Central London County Court on Tuesday, where a decision is expected on the legality of the new constitution.
Following the change in the constitution, millionaire Asian businessman Mo Chaudry said he would apply to join the party to "fight them from the inside".
But he was told his application would be blocked. Speaking ahead of Tuesday's hearing, Mr Chaudry, 49, from Newcastle-under-Lyme, Staffordshire, said: "I'm hoping the court will take a robust approach and question the real intent of the change in the constitution.
"They have no real intention of allowing people like me into the fold. It is just a camouflage to appease the system."
Pakistan-born Mr Chaudry, who is worth £60 million, runs a string of businesses around Stoke-on-Trent, which has eight BNP members on the city council.
The decision to change the BNP constitution came after the far-right party held an extraordinary general meeting in Essex on February 14. Following the meeting, BNP leader Nick Griffin said he soon expected to welcome the party's first non-white member, a Sikh called Rajinder Singh.
Lawyers from the EHRC have been considering the precise wording of the new rules to decide whether they believe the constitution is still discriminatory
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