Angry fans contacted the police following a comment posted on the 23-year-old defender's official Twitter page.

Twitter user WillMadine94 tweeted 'You big fat n***** u r s***. Martin Kelly over u all day for england. Play for africa!!!' on the footballer's page.

Mr Richards later replied on his page OfficalMR2: 'Love the racist abuse. Keep it coming.'

The matter is being investigated by Lincolnshire Police, who believe the offender to be from the Lincolnshire area.

The force thanked fans for reporting the matter to them and said on their Twitter page: "Thank you to all those who helped earlier - we will not tolerate racist comments. Also a warning to all that deleting comments does not work.''

Today the user's Twitter account was unavailable.

A spokeswoman from Lincolnshire Police confirmed that they had received reports of the abusive comments from the user and that inquiries were ongoing.

A spokesman for Manchester City said they were aware that police were investigating the matter and did not want to comment further on the incident at present.

A Premier League spokesman said tonight: "The Premier League and our clubs are opposed to all forms of discrimination and, when appropriate, it is right that the authorities take action in this area."