Conservative MP Ann Widdecombe and three other patrons of the National Bullying Helpline have resigned after the charity claimed its anti-bullying helpline had received calls from Downing Street employees.
Widdecombe joins TV presenter Sarah Cawood, workplace stress expert Cary Cooper and Mary O'Connor, a Conservative councillor in the north-west London borough of Hillingdon, in stepping down from the charity after the claims by Christine Pratt, its chief executive.
A fifth patron named on the charity's website, singer Mz Bratt, said she had never taken up the role, leaving the organisation without any patrons.
Widdecombe said she had resigned because she was concerned about the breach of confidentiality. But she said she had resigned with great regret, and wished everyone involved in the charity well.
Pratt, founder of the helpline, said she contacted the BBC at the weekend because she was angry that ministers had denied claims of bullying made in a new book by Andrew Rawnsley, a journalist at The Observer.
But she has been criticised by The Helplines Association and another bullying charity and the charity is being investigated by the Charity Commission.
The National Bullying Helpline was unavailable for comment.