Football fans may be arrested for making fun of players they believe are overweight.
The warning comes after Derby County supporters chanted insults at Coventry defender Paul Williams at Pride Park.
Derby's football liaison officer Sgt Colin Nellist says similar abuse may land them in jail. The move is backed by the Premiership club and a supporters' group.
Fans sang "Who ate all the pies?" at Williams.
Sgt Nellist said: "The behaviour was outrageous and unsportsmanlike. We will not tolerate this.
"The fans need to know that, if they do it again, they will be arrested for public order offences. They should grow up."
Some fans, however, think players should be able to take the taunts.
Rob Green, of Chellaston, said: "It's a shame Williams can't take a bit of stick, especially as he left Derby for Coventry."