The news follows the revelation in his autobiography Raw, published this week, that he was sexually assaulted and maltreated throughout his childhood.
The free-phone helpline, which is staffed by professional counsellors, has received 9,000 calls since it was set up in November 2002 by the National Association for People Abused in Childhood.
"Adult survivors of abuse carry all kinds of mixed-up feelings around, which take a long time to sort out," said Worrall Thompson. "If the helpline had been around when I needed help, I would have known that I wasn't alone."
The helpline was established with a £43,000 grant from Lloyds TSB Foundation, and the charity also received £20,000 from the Body Shop Foundation after a Third Sector report about the new venture (4 December 2002).
However, funds are now low and the charity will be forced to scale back its services drastically if it can't raise the £500,000 needed for the next three years.
The charity is hoping to secure some Home Office funding because the service is popular with people who come into contact with the police and prison service.