The former Prime Minister played a key role in the successful campaign to keep Scotland in the UK during 2014. However Nicola Sturgeon is demanding another poll by the end of 2023.
Mr Brown noted the rise of nationalism is a Europe wide phenomenon, making it “the dominant ideology of our age”.
Writing for the Daily Telegraph he said: “We thought this clenched fist nationalism had ended in the first half of the twentieth century.
“But, in our time, it has reappeared all over Europe: in the propaganda of Le Pens’ remodeled French National Front, Germany’s ADF, Italy’s League of Brothers, the Wilders party in Netherlands, and even in social democratic Scandinavia.
“Political nationalism has become, once again, the dominant ideology of our age.”
In last month’s Scottish parliament elections, the SNP fell one seat short of a Holyrood majority.
In total more Scots voted for pro-UK parties in the constituency poll than nationalist ones.
However Ms Sturgeon is hoping to get another independence referendum through the Scottish Parliament with Green Party support.
Boris Johnson is opposed to a second referendum, arguing the SNP should focus on Scotland’s coronavirus recovery.
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This would be a rerun of the 2017 contest, which Mr Macron won by 66 percent of the vote to 34 percent.
However polling suggests the 2022 contest could be much closer.
Mr Brown called for an “enlightened” British patriotism to combat Scottish nationalism.
He said: “If we are to avert years of constitutional upheaval, we have to show we can make Britain work as a political community, building on the kind of cooperation we have seen between our four nations and regions in delivering mass vaccination.
“There is indeed a golden thread that connects our centuries-old British commitment to tolerance and liberty with modern ideas of fairness and social responsibility.
“We have to rediscover that shared ethos and with it a shared mission, shared objectives and priorities; in other words, an enlightened patriotism that makes Britishness about more than holding a blue passport.”
Senior SNP figures have suggested a second Scottish independence referendum could be held even without Westminster’s consent.
Should this happen Douglas Ross, the Scottish Tory leader, is urging unionists to boycott the poll.
In 2014 Scotland voted to remain part of the UK by 55 percent of the vote to 45 percent.
Ahead of the referendum senior SNP figures indicated it would be a “once in a generation” poll.