It is claimed Lindsay was drinking as she held a house party on her roof terrace with her friends, where she was seen smoking and drinking out of a plastic cup.
While it has yet to be confirmed that Lindsay tested positive for alcohol, her father Michael blames her friends if the reports are true.
He said: "She is under a lot of pressure and there is a bad influence around her."
Earlier this week, the 24-year-old star vowed she no longer consumed alcohol and didn’t keep intoxicating beverages in her home.
She said: "When my friends come over, they're not drinking. Alcohol is not in my house, so it's just not a part of my life."
Lindsay was sentenced to three years probation, 120 days in jail and 480 hours of community service after taking a necklace from an upmarket Los Angeles boutique and breaching the terms of her 2007 probation.
The 'Mean Girls' star - who pleaded no contest to stealing the $2,500 piece of jewellery - will carry out her community service at a downtown Los Angeles women's shelter and undertake janitorial work at the county morgue.