UK Independence Party leader Nigel Farage leader campaigns for Brexit in Sittingbourne on June 13, 2016. 

Britain's opposition Labour Party today scrambled to make the case for Europe to its members as world stock markets slipped amid concern over a British exit from the EU in a knife-edge referendum next week. / AFP / CHRIS J RATCLIFFE        (Photo credit should read CHRIS J RATCLIFFE/AFP/Getty Images)