A no-deal Brexit could lead to the break-up of the UK, the ex-president of the European Council has warned.
Herman Van Rompuy told the Observer leaving the EU without a deal posed an “existential threat” to the UK.
He added a no-deal scenario would have a “big impact” on “regions such as Scotland”.
First Minister Nicola Sturgeon has previously said she will decide whether to back a second referendum on independence by the end of 2018.
Mr Van Rompuy’s comments come after the government published its first set of documents setting out no-deal advice for UK businesses and public bodies.
More documents are expected in the coming weeks – and Downing Street has scheduled a cabinet meeting to co-ordinate planning for the middle of September.
Currently, mid-October is seen as the likely deadline for an agreement setting out the terms of UK-EU divorce.
Speaking last week, UK Brexit Secretary Dominic Raab said reaching an agreement with the EU was still the most likely outcome – but preparing for other scenarios was the “responsible” thing to do.
Mr Van Rompuy said that discussion amounted to “nationalist rhetoric that belongs to another era”.
The former Belgian prime minister added that he believed no-deal comments from government ministers were part of “operation fear”, intended to scare the EU into compromising on a deal.
Former UK Brexit secretary, David Davis, has also accused the UK government of scaremongering over the implications of a no-deal Brexit in a tactic which he argues undermines the UK’s negotiating position.
Writing in the Sun on Sunday newspaper, he said a warning from Chancellor Philip Hammond that such a scenario could hit GDP by up to 10% was “an attempt to frighten the population into imagining the most terrible consequences of leaving the EU without a deal”.
‘Good deal’ confidence
A Downing Street spokeswoman said: “We have always said the United Kingdom would continue to thrive in the event of a no-deal Brexit.
“But we are confident of getting a good deal – one that delivers for every part of the United Kingdom and takes back control of our money, laws and our borders. That is what this government will deliver.”
Scotland’s Brexit secretary, Michael Russell, said Mr Van Rompuy’s comments underlined the Scottish government’s own warnings about the “catastrophic” implications for jobs, investment and living standards of a no-deal Brexit.
He said: “The UK government should instead commit to staying inside the customs union and single market – the biggest such market in the world, which is around eight times the size of the UK market alone.
“It is extremely concerning – and irresponsible of the UK government – that the whole basis of our economic relationship with the European Union and critical issues such as customs arrangements have not been agreed, with the clock ticking towards an EU exit in March next year.
“It is also deeply concerning that the potential chaos of a no-deal Brexit is now seen clearly by just about everyone concerned – including the former president of the EU Council – except the UK government.”