George Clooney has warned teen star LINDSAY LOHAN she is heading for a career slump - because nobody can stay successful for ever.

Lohan is a huge star at the tender age of 19, but Clooney insists she'll never maintain her intense level of achievement for the next 50 years.

The actor - who didn't find fame until he was 33 - says, "You can't remain totally famous over a long period of time. Lindsay Lohan is going to have a low point in her career.

"I don't know her at all, she may be completely together. What I mean is, I wouldn't have been prepared for the down period if I hadn't gone through it for a long time before my career really took off."