Ke$ha's mother Pebe Sebert tells PEOPLE mag that her 26-year-old daughter's advisers, including her producer Dr. Luke, made her feel like she desperately needed to lose weight.

Sebert claims, "Dr. Luke had been telling her how she had to get in shape and lose weight and all this stuff. She was exercising and dieting and ultimately doing everything she could, but not getting thin fast enough. And that's when she first became bulimic."

Ke$ha's mom adds:  "Dr. Luke told a friend of ours he thought she looked like a refrigerator on her latest video, and could she please try to control her weight.After she went on a 14-day juice cleanse, he said, 'Thank God you finally got rid of the weight! We've all been talking about it!' So she felt like she couldn't trust anyone."

The turning point came just before the holidays: "Right before Christmas she had a breakdown, and called me from the gas station after she'd thrown up everything, and admitted how much she'd been doing it."

But in an exclusive statement via his rep, Dr. Luke denied Sebert's allegations.

"These statements and allegations concerning Dr. Luke are completely false.

"It is unfortunate that at a time Ke$ha is suffering immensely and trying to heal at a treatment center, her mother is taking this approach with the media. I give Ke$ha my utmost support and well wishes for a quick return to health."