The former England left back, 33, is on holiday in LA after being left out of Roy Hodgson's World Cup squad.
Cole allegedly poured champagne over MTV presenter Donatella Panayiotou, shouting: 'You know what this is for!'
Cole is on a holiday with Shaun Wright-Phillips and some others, and was at a VIP party at trendy Hollywood nightclub Lure to celebrate LA Lakers star Nick Young's 29th birthday - other guests included rapper Drake and R&B singer Brandy.
Dozens of stunned revellers witnessed the incident – with one saying it resembled a “saloon bar brawl”.
The clubber said: “The whole bust-up came out of nowhere.
'Ashley’s group were spending a fortune knocking back the drinks. At one point Ashley and Donatella were at the same table and drinking happily.'
Donatella, 29, reportedly once had an affair with Manchester City winger Scott Sinclair, and claims that Cole suddenly confronted her and poured champagne over her head. 'Donatella was stunned by his outburst,' added the witness. 'They went at each other and had to be separated.'
She is also believed to have slapped Cole in the face and was heard to be shouting: ‘I’ve never done anything to you, as the row spilled out onto the streets. Donatella has now contacted the police, telling officers she was pushed and shoved during the row as well as having her throat piercing ripped out.
She refused to comment about the alleged incident but told the paper: 'There was an incident and it is now in the hands of the police authorities following a formal complaint of assault against Ashley Cole.'
Cole, who left Chelsea after the club decided not to extend his contract, is thought to be chasing a move to the US and Major League Soccer.
LAPD confirmed they are investigating the incident, which has been listed as a 'simple battery'. However the offence includes strict penalties, with up to six months in prison, a maximum $2,000 fine, community service or three years of probation. If charged and found guilty, Cole could potentially be banned from getting a working visa - leaving a move to the MLS out of reach.