The National Bullying Helpline, which was at the centre of a storm after its founder claimed it had received calls from staff at 10 Downing Street, has shut down.
The charity, set up in 2007, said in a statement on its website that it was closing with immediate effect because of a lack of funding and the resignation of Christine Pratt, its founder and chief executive.
An increased workload and attempts to secure funding for the charity had taken their toll on Pratt's health over the past year, the statement said.
The charity suspended its helpline in February 2010 after Pratt made the claims about Number 10 when Gordon Brown was Prime Minister.
She was criticised for a breach of confidentiality and all four of the charity's patrons, including Conservative MP Ann Widdecombe, resigned.
The Charity Commission opened a statutory inquiry into the charity.
A statement from the charity's trustees said that calls to the helpline had trebled in number over the past year and it had had to take on additional volunteers and resources to meet demand.
"Without doubt, this demonstrates that a free anti-bullying helpline is a much-needed and much-valued lifeline for the general public - adults and children alike," it said.
"Undoubtedly, the closure of our charity will be a great loss to the public."
The charity's website will remain in place to help people who want information and guidance about dealing with bullying. The Charity Commission is being informed about the closure and volunteers at the charity's offices in Swindon have been told.