Boris Johnson once said a Scottish person should not be allowed to become Prime Minister because "government by a Scot is just not conceivable".

Writing in the Spectator in 2005, Johnson said that it would be "utterly outrageous" if the then Chancellor Gordon Brown succeeded Tony Blair as prime minister, on the grounds that he is Scottish, The Scotsman has reported.

Mr Johnson is frontrunner in the race to succeed Theresa May as leader of the Conservative Party and become Britain's next PM.

"The Labour machine will try, at some point in the next few years, to insert Gordon Brown," Johnson wrote.

"That would be utterly outrageous, not just because he is a gloomadon-popping, interfering, high-taxing complicator of life, but mainly because he is a Scot, and government by a Scot is just not conceivable in the current constitutional context."

Johnson also claimed that Brown was "not really interested in British values" but instead in "his personal political disability as a Scottish MP."

Last week, Business Insider revealed that when Johnson edited the Spectator, he authorised the publication of a jocular poem describing Scottish people as vermin who should face "extermination."

Responding to the report, First Minister Nicola Sturgeon tweeted: "I think he’ll probably find we think the same about him."