The British National Party has attacked the "Zionist" UK Independence Party because of its support for Israel.
In a statement posted on its website, the BNP said Israel treated Palestinians as "less than human."
And it said Nigel Farage's Ukip had "sold out to the Zionist lobby."
Ukip spokesman Gawain Towler questioned whether anything Nick Griffin's party said was taken seriously.
Asked to respond, he told The Huffington Post UK: "You can have 'it's laughable'.
"That's all you're getting."
The BNP article, titled 'Beware Ukip Zionists', said: "Ukip still promotes the “brave, little Israel” propaganda so beloved of elderly Zionists. They would have you believe that Israel is a beacon of democracy which only defends itself from attack.
"Yet we know that Israel is an aggressive military power that treats the Palestinians as less than human. Palestinians are prisoners in their own country forced to live behind walls and barbed wire and show passes to get through.
"They are strangers in their own land. What nationalist could not feel sympathy for their plight? What nationalist could say that the Palestinians did not have the right to their own state on their own land?
"Ukip speak of “political dialogue” between the Palestinians and Israelis but rule out any measures that other nations might take to pressure Israel to negotiate."
Related on HuffPost: