Nike produced special wristbands for the Stand Up, Speak Up campaign set up by Arsenal's Thierry Henry.
Customers are asked for a minimum donation of £1.50, 75 per cent of which will go to the King Baudouin Foundation in Belgium, which will distribute the money among European groups working to combat racism in football.
The wristbands have been hugely popular, with Nike unable to meet demand in many parts of the country. But a number of charities believe it is wrong to accept the money.
Spanish anti-racism football campaigner Carlos Ferreyra Nunez said: "We could desperately use funds to run a countrywide campaign, so Nike's money is very tempting. But we have reservations on ethical grounds."
Mike Duncan from No Sweat, the anti-slave labour charity, agreed: "It's fantastic hypocrisy from Nike, which makes millions of pounds from black workers around the world who sweat it out to produce its goods."
Nike has been accused by the Clean Clothes Campaign of being complicit in the suppression of trade union activity in Thailand. A spokeswoman from Labour behind the Label, which is part of the campaign, said: "Although it's good to see Nike get involved in the campaign, it still needs to make improvements in the way its garments are produced."
Nike did not consult Kick It Out, the main UK group campaigning against racism in football, whose press officer Leon Mann said: "This isn't going to harm Nike, but for us the issue is how much money this could raise to benefit worthwhile causes."
Nike was asked to respond but did not do so.
Thierry Henry came up with the idea for the Stand Up, Speak Up campaign after a racial slur by Spanish coach Luis Aragones
The campaign is supported by Rio Ferdinand, Carlos Puyol and Ronaldinho
2.5 million wristbands have been sold across Europe
700,000 have been sold in Britain alone
The campaign has come in for widespread criticism as a result of concerns from charities about Nike's record on labour rights.