Interesting question. According to the Rev Ken Horleston, vicar for St Clement's Church in Horsley Derbyshire, the answer is simple - you can't!
Speaking to the Derbyshire Evening Telegraph the Rev Horleston said: "The bible calls on people to 'love thy neighbour' but the BNP's views are in violation of this.
"A person cannot be a practising Christian and vote for the BNP."
The BNP held Red, White and Blue, near Denby, in July, and wants to hold it there again next year and in 2009.
The Vicar has called for opposition to British National Party plans to hold its annual festival in Derbyshire for the next two years. He told the paper that he felt guilty for not doing more to stop this year's event and had the backing of the area's other vicars in saying Christians should not support the BNP.
Good for you Vicar.