A video of Jeremy Corbyn criticising Zionists for lacking “English irony” has reignited the debate about antisemitism in the Labour party. Given that Shami Chakrabarti’s report into antisemitism warned about “Zionist” being used as a stand-in for “Jew”, there is rightly criticism of his language.

But the former chief rabbi Jonathan Sacks has won the hyperbole sweepstakes by branding the comments the most “offensive” by a British politician since Enoch Powell’s infamous “rivers of blood” speech. The claim is as ridiculous as it is offensive – it takes a special kind of amnesia to forget just how racist and divisive that speech was.

“Rivers of blood” was delivered in opposition to the very first piece of race relations legislation in the country, the Race Relations Act in 1965, which was so weak it has had to be amended numerous times since. The speech invoked images of race war,“wide-grinning piccaninnies” and old white women being afraid to leave their houses because of the scourge of criminal immigrants. Comparing Corbyn’s comments to “Rivers of blood” obscures both the racism of the speech and the fact that it was far from an isolated episode in British political history.

Britain has a serious problem with racism in politics, and the unfortunate truth is that, even if Corbyn meant his comments in their most vile form, they probably wouldn’t rank in the top 50 most offensive by a frontline politician. To pick out just a few high-profile examples, in 1978 Margaret Thatcher claimed the nation was being “swamped” by black and brown immigrants, language that the then defence secretary, Michael Fallon, again used in 2014, when explaining communities were “under siege” by hordes of migrants. It was only in 1990 that Norman Tebbit suggested that British Asians needed to pass the “cricket test”, supporting England to prove that they belonged to the nation rather than “harking back” to where they “came from”. In 1997, Ann Widdecombe joked that the home secretary, Michael Howard, had “something of the night about him”. Given that Howard is of Jewish heritage, it is not difficult to see how loaded some people might interpret that as being. Worse still, the jibe stuck, and Widdecombe remained unrepentant.

And it’s not just the Tories who have been guilty of racist commentary. As prime minister, Tony Blair suggested that there was something distinctive about black culture that led to violent crime, and in 2009, Gordon Brown proudly proclaimed he wanted to create “British jobs for British workers”. The emergence of Ukip has poisoned the political discourse on migration to the point that the left and right are indistinguishable on the issue. Politicians have yet to work out that when Nigel Farage is calling the tune, it is best to stop dancing.

After David Cameron took office he used the dispatch box to try to smear Sadiq Khan in his run for London mayor by incorrectly claiming, in April 2016, that he shared platforms with an Islamic State supporter. While Theresa May is very careful with her choice of words, she has presided over the “hostile environment” that included vans telling illegal immigrants to “Go home”, mass deportations and the Windrush scandal, which has devastated the lives of countless people with the legal and historic right to be a part of the nation.

That’s not even to mention the offender-in-chief, Boris Johnson, whose lowlights include: invoking Powell by referring to black people as “piccaninnies” with “watermelon smiles”; published articles claiming that black people have lower IQs in the Spectator when editor; and, just the other day, causing a furore over his comments about Muslim women and the burqa.

The problem of racism in British politics runs to the core of the establishment. By highlighting Corbyn’s comments as some sort of aberration we legitimise the countless examples of racial discrimination in both words and deeds committed by British politicians. Amid the debate around Labour and antisemitism, we should not avoid a serious examination of the issue of racism that runs through the history of all the major parties and the institution as a whole. Of course we should condemn any politician for using racially offensive language, but we have already lost the battle if we pretend that such ideas are the exception and not part of the norm of British political life.

• Kehinde Andrews is associate professor in sociology at Birmingham City University and author of Back to Black: Retelling Black Radicalism for the 21st Century