The former Labour Prime Minister fears Scottish, English and Welsh nationalism will tear the country apart. Mr Brown highlighted the fate of the UK cannot be ignored in the Tory leadership contest for the next Prime Minister. He added the UK is the world’s most successful example of multinational co-operation.
Mr Brown noted a recent poll showed 59 percent of the Conservative Party would sacrifice a union with Northern Ireland “to secure the Brexit they want”.
He went on highlight 63 percent are prepared to sacrifice a union with Scotland.
Mr Brown wrote in The Daily Mail: “The Union that is the United Kingdom is in mortal danger — more imperilled now than it has ever been in its 312 years of existence.
“In the past five years, the political discourse in all of our nations has become more extreme, more divisive and more toxic.
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“But now the Union faces an existential threat: that of competing, antagonistic nationalisms within it.
“At stake is not only what kind of Brexit we are to have, but what kind of Britain we are to become. Crucially, too, the fate of the Union cannot be ignored in the contest for our next Prime Minister.
“Scottish nationalism, plus English nationalism, plus Welsh nationalism, plus Ulster unionism, does not add up to a United Kingdom — even one united only in name.”
His comments come after the nation is divided following the Brexit vote.
Mr Brown took aim at Boris Johnson who he claims is opposed to “the three constitutional pillars upon which today’s union is built — Scottish parliamentary representation, the devolution settlement and the funding arrangements”.
He said: “First, Scotland is, Mr Johnson has repeatedly said, grossly over-represented at Westminster. Yet this ignores the fact that in almost every great political union — America, Australia and Canada, for example — special allowance is made to safeguard minorities.
“Second, he opposes — and has even said he wants to strip away — devolved powers that the Scottish Parliament already has, specifically those relating to universities and social care.
“And, third, he calls ‘reckless’ and ‘unfair to England’ the established principle of funding Scottish services: the 40-year-old settlement which, with all-party agreement, allocates resources by taking account of differing needs and changing demography.”