This pitched battle is clearly a precursor to the 2012 elections, but it is also the latest shot across the bow of union purists who are relentless in waging a war against government and business for the benefit of their members.

CNN: Unions have to make concessions

Mr Galloway's Respect Party anti-war campaign captured thousands of Muslim votes in the east London constituency of Bethnal Green and Bow where 40% of the electorate is Muslim.

BBC: NEWS | UK | UK Politics | Record number of new minority MPs

Mrs Clinton has resisted pressure to bow out of the race, despite Mr Obama's growing advantage in terms of delegates and her rapidly dwindling campaign war chest.

BBC: Clinton wins W Virginia primary