"Tomb Raider" star Angelina Jolie is rumoured to be the prime factor behind the recent split of Hollywood couple Brad Pitt and Jennifer Aniston.

Although the "Ocean's Eleven" star and his wife denied media speculations about their official separation after four-and-a-half years of marriage, imdb.com reported that Jolie's involvement in the matter is widely known.

British newspaper News Of The World was told by a source that Aniston, 34, heard Pitt and his "Mr. & Mrs. Smith" co-star Jolie having phone sex.

"They would speak on the phone all the time. Jennifer listened in on the conversation. I don't know if she accidentally picked up the phone or deliberately did that. Either way, she went ballistic," the source was quoted as saying.

Arguments between the couple over the issue of starting a family have also been advanced as reasons for the split. Pitt, 41, is reportedly keen to become a father while former "Friends" star Aniston wants to concentrate on her film career.

The British tabloid Daily Star wrote that the marriage collapsed because Pitt adores playing father to Jolie's adopted son, Maddox.

An insider told the publication, "Jen became furious when he pointed out that at 29 Angelina is six years younger than her and is managing to combine motherhood and a successful career."