Robert Pattinson has told Kristen Stewart that she "completely humiliated" him by cheating with 'Snow White and the Huntsman' director Rupert Sanders.

The 'Twilight Saga' stars' off-screen relationship has hit a rough patch after she admitted that she had cheated on him with 'Snow White and the Huntsman' director Rupert Sanders.

According to reports Robert thinks that "all the trust has gone" after he found out about her affair.

A source told the Daily Mirror newspaper: "Rob is devastated and deeply hurt.

"They spoke on the phone and he said 'You've completely humiliated me'. All the trust has gone."

Robert, 26, has been dating his 22-year-old co-star for three years told him the fling was just a "one off".

He demanded she apologise for her involvement with the 41-year-old film boss and she agreed.

She said in a statement: "I'm deeply sorry for the hurt and embarrassment I've caused.

"This momentary indiscretion has jeopardised the most important thing in my life, the person I love and respect the most, Rob. I love him, I love him, I'm so sorry."

The source added: "Robert wanted the world to know that he hadn't done anything wrong and that she had made a fool of him publicly.

"He still can't fathom why she cheated. Kristen is begging for another chance. Robert is undecided."

An American magazine revealed it had pictures of the pair "in a marathon make-out session" in Hollywood.

The father-of-two's model wife Liberty Ross, 33, is also furious about the fling. Kristen is reportedly writing to her to say sorry.