Addressing the party faithful in a Swansea pub, he said that a revolution was coming, and that it was the party's role to "lead our people to the light".
The presence of the controversial politician in Swansea led to a noisy demonstration in the street outside the Landore inn, with protesters outnumbering supporters.
The Evening Post was the only media organisation to attend Saturday night's meeting at The Globe, which attracted around 65 activists from as far afield as London and Liverpool.
In a room above the bar, the party leader began by saying that mass immigration was destroying Britain and was "grotesquely unfair" to working people.
He said that unless migrants spoke English or Welsh they should not get access to benefits or schooling, and he called for a ban on building mosques — adding that the Koran was a fundamentalist book "about conquering other people".
But most of the MEP's speech was about the state of the economy, and how "they" — the political elites in charge — were intent on destroying the country.
He said: "The bankers crash has scarcely started — it is going to be truly horrible, and the Tory party cuts are not going to help, they are going to make it worse." He warned of a coming 1930s-style depression.
He went on to say that institutions such as the family, schools, the health service, council housing, and the Post Office were being deliberately undermined and privatised by a combination of hard-left activists and multinational business.
He also said Britain had been deliberately "de- industrialised".
He concluded by telling supporters that the party was on the "hard road" that would eventually lead to revolution and power.
He said: "The night is always darkest just before the dawn, but the dawn will come, and we will lead our people to the light."
He urged members to work to become community leaders ahead of the revolution.
While the leader talked, a group of around 80 anti- fascist protestors gathered near the pub.
Police blocked both ends of Mysydd Road and kept the protestors — some of whom wore masks — at one end of the street.
Among the crowd was David Phillips, leader of the Labour group on Swansea Council. He said: "Nick Griffin and the BNP are not welcome here — the people of Swansea do not support them and do want them here."
Chief superintendent Mark Mathias said he was happy with the policing arrangements.
He said: "Everybody has the right to express themselves peacefully, and the police presence was purely to ensure that the peace was kept."
He also thanked the people of Mysydd Road for their patience during the operation.
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