Mr Griffin faced angry protests when he tried to speak in London
Protesters have gathered outside a pub in Manchester where the BNP leader Nick Griffin is to hold a news conference.
Mr Griffin was forced to abandon a similar event outside Parliament on Tuesday after he was pelted with eggs.
Mr Griffin, who has been elected to the European Parliament for the North-West region, called on other political leaders to condemn the attacks on him.
But Gordon Brown told MPs that mainstream parties needed to expose the BNP's "racist and bigoted" policies.
At prime minister's questions, he called on all parties to "unite" to fight the BNP by showing they had solutions to pressing issues such as employment and housing.
And Conservative leader David Cameron said the battle against the BNP must be fought "doorstep to doorstep".
About 50 protesters have congregated outside the Manchester pub where Mr Griffin is planning to speak.
There is a heavy police presence there after Tuesday's chaotic scenes in London, when a BNP briefing broke up soon after starting in the face of angry demonstrators.
Mr Griffin said the fact that he was being prevented from speaking was a threat to democracy.
As well as Mr Griffin, a second member of the BNP was elected to the European Parliament on Sunday, for the Yorkshire and Humberside region.