Campaigners estimate more than 2 million British expats would face a major upheaval in their lives if Britain was to leave the European Union.
A Brexit would mean a huge headache for expats who would find that they are no longer allowed to live or freely move about the EU.
Other issues that would need immediate action would include sorting out healthcare, pension rights, visas, property ownership and tax residence.
These and many other factors affecting day-to-day life would have to be negotiated – possibly on a country-by-country basis – which could mean years of financial uncertainty.
Expat groups around the world, but especially across Europe, are galvanising into action to register to vote in the UK in-out referendum on June 23.
Private health cover fears
George Cunningham, who heads the Brits Abroad: Yes To Europe campaign is urging expats to add their weight to the yes vote.
“Any British expat who has lived away from the UK for less than 15 years is entitled to cast a vote in the referendum,” said Cunningham.
“Those the that can’t vote should still do all they can to encourage others to take part in the referendum. There is no reason why any expat should not vote to stay in the European Union. Anything ese is madness.”
One of the biggest fears for expats is losing the benefit of health cover in the EU if Britain leaves.
Visa loss could destroy careers
Anyone that qualifies for a European Health Insurance Card (EHIC) would no longer have free health cover and would have to take out expensive insurance or pay for the service.
“Many elderly expats would find health care unaffordable and those who are in work would lose their visas, which could damage their careers as many work across borders,” said Brian Cave of expat web site Votes for Expat Brits
Meanwhile, in the UK, Prime Minister David Cameron and Chancellor George Osborne face a split in the Tory party and some unlikely ‘Stay In’ bedfellows.
Labour, the Lib Dems and Scottish Nationalists all want to vote to stay in the EU, while more than 100 of the 315 Tory MPs at Westminster have declared their opposition.