Prime Minister David Cameron may be planning to make a last-minute pledge to hold a referendum on Turkish European Union (EU) membership in a bid to stop Brexit.

The Financial Times says that if ‘Leave’ continues to gain momentum in the run-up to the EU vote later this month, David Cameron could make the pledge in a desperate bid to take the wind out of its sails.

Such a promise would echo the run-up to the 2014 Scottish independence vote when Westminster political leaders made a desperate set of “pledges” in the last days of the campaign after a rogue poll put the pro-independence camp ahead.

France and Austria have already promised their citizens a referendum before they allow Turkey to join the EU, and Cameron may follow suit as the Leave campaign highlights the threat of mass Turkish immigration.

Mr Cameron may hope that such a move would sabotage one of Leave’s strongest arguments, however it would also be a tacit admission that Turkish accession is a real possibility in the near future.

The British government’s official policy is still to support Turkey joining the bloc, while German Chancellor Angela Merkel has appeared desperate to heal relations with Turkish President Recep Tayyip Erdogan.

The rumours come as Leave gains ground in the EU referendum with the focus turning to immigration.

A poll last month found that immigration is the top issue for undecided voters in the referendum debate, with 28 per cent telling a Sky News survey it was their biggest concern, compared to just 15 per cent who cited the economy as their main issue.

The Leave campaign has begun focussing on immigration in recent weeks, with the result that it now has momentum in the polls and is either taking the lead of closing the gap with Remain among the various polling firms.