The 28-year-old man was arrested after pictures taken during the Blues' League Cup fourth-round victory over United on October 31 appeared to show him directing the gesture at Welbeck.

But after examining CCTV footage of the incident and interviewing other fans in the crowd, Metropolitan Police and the Crown Prosecution Service have decided not to bring charges.

"The Metropolitan Police Service (MPS) takes any allegation of racist chanting and/or behaviour very seriously and if any matters are brought to our attention they will of course be thoroughly investigated," a Scotland Yard spokesman said.

"The MPS routinely work very closely with football clubs and partner agencies to monitor behaviour to ensure public confidence and safety."

Last December Chelsea vowed to ban any fans found guilty of racist abuse after Daniel Sturridge was allegedly the target of racist chants, and earlier this year a supporter received a lifetime ban after admitting to abusing former Blues striker Didier Drogba.