Actress Lindsay Lohan has defended her West End theatre debut after she was accused of forgetting her lines in her first show, insisting the performance "could have been a disaster... but it wasn't".

The "Mean Girls" star began her first theatre run in a London production of David Mamet's "Speed-the-Plow" Wednesday night, but the audience claimed she stumbled through the first preview performance and struggled to remember her lines.

However, Lohan is insistent she is happy with her first night on stage, reports contactmusic.com.

"It could've been a disaster, but it wasn't by far... Everyone is always going to be judgemental, no matter what. I respect people have an opinion, but I'm doing the best I can and will for the duration...," she said.

"I was nervous on the first night because I'd never done it before. But everyone (working on the show) has been really great... they've all been very kind, gracious and comforting," she added.