Lindsay Lohan's ex-girlfriend Samantha Ronson has been charged with misdemeanour DUI.

The 33-year-old DJ - who was arrested last Monday while driving her black Porsche back to Los Angeles from a gig in Las Vegas - has been charged with two counts of DUI, driving under the influence and driving with a blood alcohol level over .08. If she were to be convicted, she could face six months in prison, but the majority of first offenders usually get probation, according to TMZ.

Samantha was arrested at 10:30 a.m. after she refused to take a breath test when asked.

It is not the first time Samantha has suffered an incident on the roads in 2011. In April, she was left with a bruised and cut face after she was knocked off her BMX bike after cycling home from a DJ gig in Los Angeles.