Actor Jude Law has denied rumours he is having an affair with Hollywood star Nicole Kidman.

He spoke out following reports his marriage to Sadie Frost was in crisis.

She has been suffering from post-natal depression since the birth of couple's third child and has been treated in hospital.

Sadie Frost and Jude Law have three children together

Newspapers reported her problems were due to her husband's close relationship with his co-star Kidman on the set of the movie Cold Mountain.

But he insists there is "absolutely no third party involved" in his marriage.

"My family and I are angry and saddened by the malicious, mean-spirited and absolutely untrue stories that have run in the press over the past two weeks," he said in a statement.

"Other than the fact that my wife has been suffering from post-natal depression - for which she has been receiving treatment - there is not one shred of truth in anything that has been written."

Fly back

Law said he was talking to his lawyers and would take legal action against anyone spreading gossip.

"There is absolutely no third party involved in our marriage. To suggest otherwise is malicious, hurtful and libellous," he added.

Kidman split from husband Tom Cruise in February 2001

Frost, 37, was admitted to Cromwell Hospital in London last week following the premature birth of the couple's son Rudy.

She has since returned home and Law has flown back from Los Angeles to be with his wife as she recovers.

Frost also has a son from a previous marriage.

The couple hit the headlines in October 2002 when their daughter, two-year-old Iris, swallowed part of an ecstasy tablet that she picked up from the floor of a members club where she was attending a children's party.

Iris was rushed to hospital but was given the all-clear because Frost had been able to retrieve most of the tablet before her daughter swallowed it.