Angelina Jolie has sparked doubts over the longevity of her relationship with Brad Pitt - by insisting a faithful union isn't "absolutely essential for a relationship."

The Oscar-winner and her Hollywood hunk partner have been together for five years, and share six children; Maddox, eight, Pax, six, Zahara, four, Shiloh, three, and twins Knox and Vivienne, 17 months.

But the actress insists that despite their commitment to each other, the pair don't expect to be "chained together" forever.

According to Britain's Daily Mirror newspaper, Jolie says, "Neither Brad nor I have ever claimed that living together means to be chained together. We make sure that we never restrict each other.

"I doubt that fidelity is absolutely essential for a relationship. It's worse to leave your partner and talk badly about him afterwards."

And Jolie admits their romance is often marred by furious arguments.

She adds, "The sparks fly at home if the nice Brad fails to see that he's wrong and reacts in a defiant way. Then I can get so angry that I tear his shirt. We're not violent enough for these things, and we consider our six children."