Boris Johnson’s main adviser on keeping the UK together has departed, saying his position was made “untenable” by others within Downing Street.
Oliver Lewis, an ally of the prime minister’s former chief adviser, Dominic Cummings, was a key part of the campaign for the UK to leave the EU.
His departure comes as the Scottish National Party is calling for another referendum on independence.
Mr Lewis was confirmed in his role just two weeks ago.
He replaced Luke Graham, a former Conservative MP.
Following Mr Lewis’s departure, Scotland’s First Minister Nicola Sturgeon, who supports Scottish independence, tweeted: “Disunity in the Union unit. Or maybe just despair at realising how threadbare the case for it is.”