Johnson, the clear favourite to win the Conservative leadership race, spelled out his views on power in the UK in the era of devolution in a blistering attack on the former Labour leader, claiming that Scotland was full of “rotten boroughs”.
Writing ahead of the 2005 general election, Johnson said it would be “utterly outrageous” if Brown replaced Tony Blair after the vote as Labour leader and consequently became prime minister.
He wrote that it was “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.”
The SNP claimed it was just “one example” of Boris Johnson showing “absolute contempt” towards Scotland.
Lesley Laird, Labour’s shadow Scottish secretary, said such “crass comments” made Boris Johnson unsuitable to lead the country.
In the 2005 diary piece in The Spectator, Mr Johnson continued: “Not only is Scotland full of rotten boroughs, where Labour MPs are returned by relatively tiny electorates but, as I never tire of saying, we English MPs can be overruled by Scottish MPs on very controversial questions, affecting our constituents, when we have no corresponding say over those questions in Scotland, and those Scottish MPs themselves have no say over those questions, so that John Reid, Scottish health secretary for the so-called UK, has no say over health questions in so far as they affect his own constituents.
“Some say this is just inside-beltway stuff. They are wrong. It makes English audiences roar with anger, and it explains why Gordon Brown makes so many speeches about ‘Britishness’ and ‘British values’.
“He’s not really interested in British values. He’s worried about his personal political disability as a Scottish MP, and so he should be.”
Mr Brown would eventually become prime minister in 2007 when Tony Blair resigned as Labour leader. He stepped down following the 2010 election.
Mr Johnson is widely expected to become the next occupant of 10 Downing Street after establishing a dominant lead in the on-going Tory leadership race.
A spokeswoman for the SNP said: “This is only one example of Boris Johnson showing absolute contempt towards Scotland. It beggars belief that he is the firm favourite to be the next Prime Minister.
“Scotland deserves better than the current crop of incapable Tories. It is clearer than ever that the only way to properly protect our interests is with independence.”