Former Kasabian singer Tom Meighan has admitted assaulting his ex-fiancee.
He pleaded guilty at Leicester Magistrates' Court to attacking Vikki Ager while drunk on 9 April.
Ms Ager hit her head on a hamster cage after being thrown across a room. The musician also grabbed her leg and hit her on the head, the court heard.
Kasabian said they were "left with no choice but to ask Tom to leave the band", adding there is "no way we can condone his assault conviction".
A child witnessed the "sustained assault", the court was told, and contacted 999 to report that a "domestic incident was taking place".
Meighan was given an 18-month community order and told to carry out 200 hours of unpaid work.
He will also be required to complete five days of rehabilitation, and was ordered to pay a £90 victim surcharge and £85 in prosecution costs.
On Monday, the group announced Meighan had stepped down from the band in order to deal with "personal issues".
Magistrates heard after Meighan "threw the victim across the room in a rage" and Ms Ager was struck on the head, he threatened to hit her with a wooden pallet before he "thought better of it, thankfully, and threw it down on the hot tub aggressively".
The court was told Meighan "smelt heavily of intoxicants" as he assaulted her.
Prosecutor Naeem Valli said the attack had left Ms Ager with bruises to her knees, elbow, ankle and "a reddening around her neck".
Meighan, of Narborough, originally denied an assault had taken place, but after watching video footage he told police he could not watch it any further because it was "horrible".
Mr Valli told the court the child "sounded panicked and afraid" while making the call and the victim could be heard saying "get off me, get off me".
He added officers described Ms Ager as being "visibly upset" while Meighan was said to be acting "aggressive" and was unwilling to co-operate.
As CCTV of the attack was shown in court, Meighan wiped his eyes with a tissue and held his head in his hands.
Defending, Michelle Heeley QC said Meighan felt "deep remorse" and a sense of "personal humiliation - but he has nobody but himself to blame".
She added he had faced a "battle with alcohol" and that "to lose the opportunity to perform with the band he loves and people he loves is a huge personal loss".
Sentencing, district judge Nick Watson said: "I need to take account of the fact that not only did you hurt Ms Ager, you also let down many people - band members and those who love your music.
"They will be shocked about what you did that night.
"Ms Ager has not made a statement to police and does not appear to support this prosecution.
"Of course, that choice does not mean I should treat this offence any less seriously."
In a statement after the court hearing Kasabian said: "No-one in the band wanted this to happen. We have all worked so hard for the past 23 years and had big plans for our future together. We're completely heartbroken.
"As soon as we found out about the charges made against Tom, we as a band made the decision that we could no longer work with him."
They added: "Ultimately, as much as Tom hurt us all, we're not the victims in all of this. Domestic violence is something that can never be excused."
Kasabian formed in 1997 and reached the UK charts with their third single Club Foot in 2004. Major success came with albums Empire in 2006 and West Ryder Pauper Lunatic Asylum in 2009, which featured a string of hits including Underdog and Fire.
Meighan's departure leaves guitarist Serge Pizzorno and bassist Chris Edwards as the only remaining founding members.