British and Commonwealth boxing champion Dereck Chisora has been found guilty of assaulting his girlfriend but has been spared jail.
Chisora, 26, from Finchley, north London, was given a 12-week prison sentence suspended for two years following the attack on 28 May.
He hit the woman after finding texts from a man on her phone, a court heard.
A jail term would have meant him missing next month's world heavyweight title bout against Wladimir Klitschko.
Passing sentence at City of Westminster Magistrates' Court, District Judge Quentin Purdy, said: "Your behaviour on 28 May was disgraceful and downright humiliating.
"You used violence on this young lady and then to heap ignominy on her you turned her over and slapped her on the bottom repeatedly."
The court was told that Chisora, who has previous convictions for assault, launched the attack after finding text messages from another man on his then girlfriend's phone.
Darren Watts, prosecuting, explained that Chisora was at the woman's home and was reading text messages while she was in the bathroom.
He said Chisora grabbed her by the arms and threw her to the bed and said, 'You cheated on me'.
Boxing promoter Frank Warren was in court and handed the judge a letter vouching for Chisora.
Chisora was ordered to pay £1,500 in compensation and £500 costs. He was also told he must complete 150 hours community work.
The judge described the attack as an "ugly incident", adding: "You clearly have a problem with violence and that has got to stop or your career will be over."
The court was told that the fighter had previous convictions for public order offences, assaulting a police officer and possession of an offensive weapon.
Philip Moy, defending, said Chisora could face further sanction as he would have to appear before the British Boxing Board of Control after his conviction.
Mr Moy explained that Chisora and the woman had now separated, and that their relationship was "not made in heaven".
Chisora is unbeaten in 14 fights but is rated a heavy underdog against IBF and WBO title holder Klitschko.