British heiress Stephanie Allen has alleged that Lohan had sex with her husband Tony in the toilet of a Utah rehab facility, The Mirror reports.
The 29-year-old, whose family is worth over $1.5 billion, has reportedly kicked the Dead Stays Alive frontman out for his infidelity.
The heiress has retained custody of the couple's eight-month-old twins.
"Stephanie's had it, period," a friend told The Mirror.
"They tried forever to have kids. She went through IVF three times and suffered two miscarriages, and when they finally got two beautiful babies, he hooks up in rehab with a girl half his age."
The musician, 39, denies he hooked up with Lohan and claims they were only friends during their time at the rehab clinic.
"We're great friends. We share a common affliction and we just talk about life sometimes," he said.
The Mean Girls star is currently in rehab at a facility in LA after she was arrested for drink-driving and drug possession on July 24.
Reports emerged earlier this week that Lohan was set to quit Hollywood because she felt it was the cause of her problems.
