London, Aug 9 - Michael Jackson's long term actor friend has confessed that he secretly donated his own sperm to help the singer have children.

Mark, 51, told News of the World, that he is convinced by the uncanny and growing likeness of 11-year-old Paris to his 15-year-old daughter Harriet that he is the father of both the girls.

The 'Oliver' star has pledged to take a paternity test to prove it, reports thesun.co.uk.

'It's been a secret for so long. In 1996, Michael asked me if I would give him my sperm and I said yes. It was a gift to him, no money was paid, it was something I was honoured to do. He wanted children so badly,' said Mark.

Mark, who now works as an osteopath and acupuncture specialist, says he is speaking out because after Jacko's death he fears he will be manoeuvered out of the lives of his Godchildren - Paris, 12-year-old Prince and Blanket, seven.