Not since two black US athletes raised their fists in solidarity with the civil rights struggle back home as they were awarded medals at the 1968 Olympics has a sporting contest been so overladen with the politics of racism as Euro 2012.

Already, the Dutch team complain that they have had to move their training matches elsewhere in Poland as black players have been the subject of racist abuse. Black English stars say their families cannot go to Ukraine for fear of meeting racism in the streets. In Baden Baden in 2006, where England stayed, the main street in the Black Forest spa had a giant banner in English saying, "Welcome and Good luck England." I watched as the Wags tottered on high heels on their daily shopping excursion. German store-keepers were interested in the colour of their money, not the colour of their soccer boyfriends' skins. Black players were treated as fellow Europeans.

Football, a sport that has done more than anything else to integrate non-white Brits as heroes of working class communities, will now be confronted with the moral test of either allowing racism in the crowds in Poland and Ukraine to surface or stamping on it so hard that the racists are forced to crawl back under their stones.

The fans come from all over Europe. Incidentally, problematic as racism and anti-Semitism are in East Europe, it is unfair to single out the two host countries. The neo-Nazi Golden Dawn party in Greece has a  following in working-class Athens where anti-immigrant feeling is part of the current turn to the extremes. The monkey sounds or the chant "Hamas, Hamas, Jews to the Gas" are heard far to the west of the Dnieper when fans want to discountenance black players or teams that have some vague Jewish connection. "I'd rather be a Paki than a Jew" is a West Ham chant and it was the Daily Mail that highlighted Avram Grant's Jewishness when the Israeli was Chelsea manager. Recently, as they pander to voters, Angela Merkel, Nicolas Sarkozy, and David Cameron have made speeches denouncing "multiculturalism". BBC Question Time provides a monthly platform for Nigel Farage to denounce immigration or the presence of too many foreigners in Britain. Why should soccer fans feel they have to be saintly endorsers of multiculturalism on the pitch or cheer immigrant players in the enemy team when their national leaders promote monoculturalism? The sectarianism in Scottish football between Rangers and Celtic fans was allowed to fester for decades with the Scottish FA and Scottish politicians and editors turning a blind eye. It is leadership, not blaming lumpen elements in supporters, that is needed.

David Cameron's shamefully late announcement that Britain would join Germany, France and other EU nations and boycott the opening matches because of Ukraine's brutal treatment of its former prime minister Yulia Tymoshenko shows how politicised the tournament has become. UEFA boss Michel Platini may whine that it is about sport, not politics, but he is contradicted by his own organisation, which has announced a programme of monitoring on racism amongst fans in the run-up to and during Euro 2012.

Rafael Pankowsky, Poland's leading campaigner on anti-Semitism and racism, has been hired by UEFA to promote what the football federation calls its Respect agenda. But UEFA has to do more than monitor or hold post-final inquiries. If there are monkey calls or other examples of racist abuse from fans, then the matches have to be stopped. The fans should be evacuated by force from stadiums and the matches played to empty stands. Nothing else will do to cauterise the continuing racism in sport. Any player who feels racially abused must be supported by Roy Hodgson and other managers, so that teams walk off the pitch with their heads high, rather than allow racist abuse to go rewarded.

In 1970, Willy Brandt fell to his knees at the Warsaw Ghetto as an acknowledgement of where racist anti-Semitism had led to in German politics. Sometimes, great public symbols are needed to turn political life in a new direction. Football is run by some of the most selfish, greediest and stupidest men on earth. But even they know racism when it is heard and chanted in their faces. Maybe, and let's hope so, Euro 2012 will be about sport, not politics. But if a player and his mates stop play, rather than suffer racist abuse, the world will be with them and so should UEFA .

Denis MacShane MP is a former Europe minister. Follow him at @denismacshane or www.denismacshane.com