It’s still spring, yet 2016 already stands out as one of the ugliest years in modern British political history. It was fantastic to see Londoners choosing hope over fear in May, electing Sadiq Khan as our first Muslim mayor. But David Cameron, having shamelessly endorsed Zac Goldsmith’s dog-whistle campaign tactics, owes those young Muslims who have been put off politics by the slurs hurled at Khan an explanation. How does racial profiling and sectarian scaremongering fit into his One Nation vision for Britain?

Meanwhile, Boris Johnson, one of the best bets to succeed Cameron as our next prime minister, embarrassed Britain on the world stage with a racially charged allusion to Barack Obama’s Kenyan heritage. And my own party has been grappling with a swath of deeply disturbing revelations regarding the attitudes held by some on the left towards Israel and Jewish people. Sowing discord by stigmatising or scapegoating a single faith group or community is profoundly at odds with the British tradition of “tolerance”, but we can’t ignore that this year’s events are part of a rising trend of friction and factionalism.

Last year’s general election should have been a wake-up call. The political and cultural divides between people living in the north and south and urban and rural areas – as well as between working-class and metropolitan sensibilities – appear starker than ever. In May’s devolved elections, Scottish, Welsh and Northern Irish politics became yet more distinct – giving the impression of a kingdom coming apart at the seams. All the while, more and more voices in our national politics seek to pin the blame for the challenges facing our country on a single section of society, whether immigrants, Muslims or another group.

This trend stretches beyond our borders. From Ukip, the French Front National and Austria’s Freedom Party to Podemos in Spain and Italy’s Five Star Movement, new populist parties of the right and left are on the rise across Europe. In the United States, Bernie Sanders is tapping into the energy of Occupy Wall Street, while Donald Trump has emerged as the heir to the Tea Party: a poster boy for division and recrimination.

Trump’s rise should be a warning for us Brits. The New York Times commentator David Brooks has described his success as less indicative of the emergence of a new school of thought, or movement, and more of dissatisfaction with the status quo. Trump’s campaign has tapped into a complex cocktail of grievances, from the loss of manufacturing jobs in a globalised economy to rising inequality and raw anger felt by many white working-class Americans at demographic and cultural changes.

In the run-up to last year’s general election, as I travelled around the country, I was confronted time and time again with the reality that in the UK – just like in the US – people are afraid and angry because the world is changing in ways they fear are beyond their control. Where once they had believed that, if they worked hard, they would get ahead, too many Britons now feel that the system is rigged in favour of those born into opportunity and that those in power have abandoned them to a broken future. What it means to be British seems to have shifted around them, triggering a crisis of solidarity.

We are at a crossroads and may face nothing less than the Trumpification of British politics. In an uncertain and changing world, it is all too easy to imagine that our problems are caused by those who are different from us.

If we wish to follow the fine example set by Londoners on 5 May and choose unity and empathy over division and blame, we must accept that simply “tolerating” one another will no longer do. There is an accusation built into the very word: what you are doing is “other” or “wrong”. As Britain has become more diverse, we have come to know each other less. This makes it harder to understand how people from different walks of life feel about the big issues.

I am a Labour member because I believe, as it says on our membership cards, that, by the strength of our common endeavour, we achieve more together than we do alone. In order to develop the bonds of trust required for this to become a reality, and for our communities to flourish and our democracy to deliver for everyone, we must build a society in which people from all backgrounds actually get to know one another and lead interconnected lives. In this sense, “One Nation” – the land over which all parties seek purchase – should become more than a platitude. It should become a way of life.