Brexit risks break-up of Union if citizens are angered by different rules across UK, warns former civil service chief

Anything from agricultural subsidies to food labelling could trigger major disputes, top mandarin predicts

Brexit risks the break-up of the UK if citizens are angered by different rules and regulations in the four nations, a former civil service chief is warning.

Anything from higher agricultural subsidies to variations in food labelling – once outside the EU’s single market – could trigger major disputes between London and the other capitals, Philip Rycroft said.

Asked if such changes sowed the seeds for the end of the Union, Sir Philip replied: “It doesn’t automatically, clearly.

“But it is out of all of those little disputes that characterise the relationship between the Scottish government and the UK government – people’s perception of how interests of Scots are being carried forward in the Brexit enterprise.”

Sir Philip, the permanent secretary at the Brexit department until March this year, warned the problems were looming when the Union was “already under stress”.

“People in Scotland will need to be convinced that the UK government is respecting the interests of Scotland in all those many post-Brexit domains – and the same thing applies, of course, to folk in Wales and Northern Ireland.”

While the UK is in the single market, it must obey commons regulations – but, once it leaves, the four nations will be free to go their own way in devolved areas.

Sir Philip pointed to both sheep subsidies and food labelling as potential flashpoints, despite being apparently minor issues in themselves.

“If the Scottish government is giving bigger subsidies [on sheep], that would put Cumbrian farmers at a disadvantage,” he warned.

And, on food labelling, he added: “That would require manufacturers to produce different labels for supermarkets north of the border, compared to south of the border.

“These things would disrupt the internal market of the United Kingdom.”

The warning comes amid inflamed tensions between Westminster and Holyrood, with Nicola Sturgeon, Scotland's first minister, having accused Boris Johnson plotting an “anti-democratic move” to “shut down parliament”.

The SNP leader has also insisted she has a “clear democratic mandate” for a second independence referendum, with the government hell-bent on a “catastrophic” no-deal Brexit.

Mr Rycroft worked for the Scottish Office and the Scottish Executive, before taking over as permanent secretary at the Brexit department in 2017.

He provoked controversy by taking early retirement on 29 March this year – the date the UK was originally scheduled to leave the EU.