Regardless of the source (who obviously have an interest in discrediting the UKIP), these allegations are very serious. The regular traffic of members between UKIP and the BNP revealed here should be worrying to all of us but especially those who voted for UKIP in the European elections.
It would not be the first time UKIP members have appeared under a 'flag of conveneience'. I know of at least one District Councillor elected as an Independent who then revealed himself as a UKIP member. That would be fine if he felt that district council work should not be a matter of party politics, as many honourable Independents do. In this case however he used his position to make anti-EU speeches and tried to get the council to refuse to pay for its memberhip of the Regional Assembly on the basis that was an EU front.
UPDATE: Broken link fixed - I hope since when i edited the post the link was shown correctly. Just in case here is the URL
http://www.britainineurope.org.uk/inyourarea/eastmidlands/news/UK%20Independence%20Party%20Links%20with%20the%20BNP%20should%20worry%20residents%20in%20the%20East%20Midlands
