It’s hard to avoid noticing that most of our political parties seem to be embroiled in rows over racism and prejudices. Two Conservative local election candidates were suspended over racist social media posts last week – and that’s after a steady drip of revelations over Islamophobic comments made by members and candidates alike. Labour suspended several local election candidates over antisemitic comments and is still accused of failing to tackle hundreds of complaints of antisemitism within the party. Now, new political parties are apparently keen to catch on. Few will have had the highest expectations of Nigel Farage’s latest vehicle, the Brexit party – or, indeed, of his old one, Ukip. But, for some, hopes were set higher with Change UK – where one candidate for the European election resigned after sexist and racist tweets he wrote were uncovered, while another did so just a day earlier, having made disparaging comments about Romanian people in 2017. Another of its candidates is accused of Islamophobia (though she has refuted this). This is the party that was accused of racism within hours of launching, in February, when one of its members referred to people from black, Asian and minority ethnic backgrounds (BAME) as being of a “funny tinge”, although she apologised.

Predictably, all of this has fuelled the never-ending political game of “your party is more racist than my party”. This depressingly superficial approach feeds into a standard response pattern. Assuming parties get beyond kneejerk denialism (granted, a big assumption - since this has been at points the response from both main parties), candidates or members making prejudiced comments are ejected or deselected, and this process is itself held up as proof of taking racism seriously. Such a response, if done transparently and speedily, is welcome and promotes trust in a complaints process. But this approach does not get to why it keeps happening – and across our political parties – in the first place.

Bigoted sentiments may not be new, but they have been validated, mainlined and presented as reasonable

You could put some of it down to incompetent or rushed vetting – especially for snap elections or unintended European elections. And it’s true that different racisms manifest in different ways in the left and right of politics. There are distinct reasons why Corbyn’s Labour is more susceptible to antisemitism and the Conservatives are dealing with complaints over Islamophobia. Still, while politics can influence social attitudes towards prejudice, it’s a two-way street. As Omar Khan, director at the Runnymede Trust, a race equality thinktank, points out, it’s not as though party candidates or members are creative in their prejudiced comments. “They don’t have random views about Jews or Muslims,” he told me. “They are the same tropes that were used hundreds of years ago.” The fact these tropes are so similar, so unoriginal, suggests they are drawn from an available supply; from society at large. Which is one reason why any party seeking to tackle prejudice should make awareness and education a key component of its approach.

Politics is no doubt also reflecting the permissibility that Brexit unleashed around prejudice – last year a UN special rapporteur said Brexit had made people “vulnerable to racial discrimination and intolerance”. Bigoted sentiments may not be new, but they have been validated, mainlined and presented as reasonable. According to the British Social Attitudes survey, a quarter of the population is consistently happy to self-define as prejudiced towards people of other races. Last year, a Guardian study exposed the shocking extent of racial bias operating in Britain. How could politics be immune from this reality? It has long manifested in the workplace, to the extent that minority ethnic Britons face “shocking” discrimination, according to research from January, which showed job seekers from minority ethnic backgrounds have to submit 80% more applications than a white person to get a positive response. You might wonder if that’s affecting party candidate selection processes, too: just six of 99 Labour general election candidates for marginal seats are from BAME backgrounds. The situation at local council level is not much better. A census before last week’s local elections showed 96% of councillors are white (while two thirds are male). From there, it isn’t a great leap to see that unconscious bias may also be failing to filter out prejudices in prospective candidates or current MPs – or just not to recognise a particular prejudice for what it is.

British politics has for decades been infused with hostility to migrants and Muslims, with both left and right governments pushing scapegoating narratives. Is it any wonder that 30% of the public now think the government has downplayed immigration figures and 18% believe the conspiracy theory that Muslim immigration is part of a takeover plan. It’s also why we have progressives from the centre to the radical left variously boosting claims of “legitimate concerns” over immigration, or holding migrants responsible for fuelling the far right by failing to integrate, or blaming Asian people for grooming gangs, or foregrounding the perceived sentiments of a working class which is – counter to the real world – implicitly and almost nostalgically white. Such attitudes have permeated our political culture, readily activated in a country with a history of colonialism and empire underpinned by racial superiority myths.

On top of which, Brexit has veered Britain into the worrying politics of majoritarianism – it drives the relentless populist invocation of the “will of the people” to deliver an EU exit (which people and who gets to define that?). It’s no surprise that this sort of politics stifles the championing of diversity and tolerance, and stunts battles against racism across the board. In this climate, it is small wonder that minorities understand this hate as directed at different racialised groups interchangeably. And it is one more factor building the case that a political commitment to anti-racism has to go much further than the lip service that seems to be the current default across all parties.

• This article was amended on 9 May 2019. An earlier version incorrectly stated that “the Conservatives did not field a single minority ethnic candidate in last week’s local elections”.

• Rachel Shabi is a writer and regular broadcast news commentator