Bill Cosby's wife has rejected sex assault claims against her husband, saying the veteran entertainer being accused by at least 15 women of drugging and having sex with them is "a man I do not know".

US comedian and actor Bill Cosby’s record of big donations to colleges and other institutions has been a key part of his rosy public image – but the rising tide of allegations made by women accusing him of sexual assault is threatening to overshadow his generosity.