Kristen Stewart has apologised publicly to Twilight co-star Robert Pattinson following tabloid reports that she had a brief but steamy affair with her Snow White And The Huntsman director Rupert Sanders.

The 22-year-old actress issued her apology to People magazine.

It was quickly followed by an apology via People from 41-year-old Sanders to his family.

Stewart has been in a relationship with Pattinson for several years. Sanders is married and has two children.

Stewart said her "momentary indiscretion has jeopardised the most important thing in my life, the person I love and respect the most, Rob".

Sanders said he is "utterly distraught about the pain I have caused my family".

US Weekly published photographic evidence of the affair in its latest issue, with the pair in steamy and compromising embraces.