Lindsay Lohan and Samantha Ronson. (WENN.COM file photos)

Lindsay Lohan was allegedly involved in a vicious public argument with her ex-girlfriend Samantha Ronson at a bar in Los Angeles on Wednesday night - which ended with the actress throwing a drink over her former lover.

The on/off couple ended their turbulent romance for good last year following a series of spats.

But the dramatic relationship is back in the spotlight again after the former lovers reportedly fell out while Ronson was DJing at the Crown Bar in West Hollywood.

Editors of Radar Online allege Lohan became irritated when she failed to gain Ronson's attention and the encounter turned nasty.

A source tells the website, "Sam was working her usual weekly gig DJing at Crown bar. Lindsay turned up around 11pm and she was in the mood for trouble! Lindsay was trying to get Sam's attention, but she was working and studiously ignored Lindsay. You could see Lindsay getting more and more worked up the more Sam didn't pay her any attention.

"Sam just got sick of it all in the end though and started taunting Lindsay about her being all drunk and messed up. That made Lindsay just totally flip out on Sam. She picked up a drink and threw it straight in her face! Sam was absolutely furious and picked up some DJ equipment that was by her and threw that at Lindsay. It was crazy!

"Lindsay's friend grabbed her and pulled her away before things got even worse."

Ronson fuelled reports of a spat with her ex-girlfriend in an angry post on her Twitter.com page in the early hours of Thursday morning. The message reads, "I'm all about turning the other cheek, but sometimes you gotta stand your ground. Warning: I ain't taking this s**t no more."