Voters in France, Italy and the Netherlands are demanding their own votes on European Union membership and the euro, as the continent faces a “contagion” of referendums. EU leaders fear a string of copycat polls could tear the organisation apart, as leaders come under pressure to emulate David Cameron and hold votes. It came as German business leaders handed a considerable boost to the Leave campaign by saying it would be “very, very foolish” to deny the UK a free trade deal after Brexit. Markus Kerber, the head of the BDI, which represents German industry, said that 1970s-style trade barriers...