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 would result in job losses in Germany.

“Imposing trade barriers, imposing protectionist measures between our two countries – or between the two political centres, the European Union on the one hand and the UK on the other – would be a very, very foolish thing in the 21st century.”