She's maintained a dignified silence so far over her ex-husband's romantic conquests, watching him jump from one young starlet to another.

But yesterday Nicole Kidman, 37, decided it was time to give Tom Cruise a word of warning - stop publicly exploiting your love life.

Speaking in next month's issue of Vanity Fair, the Cold Mountain star was careful not to pass judgment on the 42-year-old actor's new relationship with actress Katie Holmes, 26.

But having seen him parade their romance in front of the press, she said:

' In terms of your life, if you start to exploit it, then what's real and what's not? What's yours and what isn't?' Last month, Cruise went down on one knee on The Oprah Winfrey Show and declared his feelings for Holmes were 'beyond cool'.

Yesterday, at the Hollywood premiere of her latest film, Batman Begins, Holmes refused to confirm or deny their reported engagement.

But she gushed: 'When Tom calls for me, I'm coming. I'm more and more in love every day.'

Kidman, who has been more subtle in her relationships, with singer Lenny Kravitz and then film producer Steve Bing, added she was still looking for someone to 'sweep me off my feet'.

• Vanity Fair is on sale on Friday.