The Charity Commission has banned the National Bullying Helpline (NBH) from disclosing any details about the nature and source of confidential calls it has received, unless it is given permission.

The Commission today opened a statutory inquiry into NBH in the wake over 160 complaints it received following the Gordon Brown bullying row.

In a statement the Commission said concerns had been raised about the protection of confidential information held by the charity as a result of the operation of the charity's helpline for victims of bullying.

A Commission spokeswoman said: “The focus of the inquiry is to ensure the trustees continue to protect this confidential and sensitive information.

“As a temporary and protective measure, the Commission has made an order preventing the transmission or disclosure of information, including details about the nature and source of the confidential calls it has received, without the permission of the Commission.

“In addition, the inquiry will cover other issues within our remit, relating to the charity's policies and procedures on data protection and confidentiality of information gathered during the course of its work, and issues surrounding referrals understood to have been made by the charity to a business connected with one of its trustees.”

NBH has reopened its helpline after closing it temporarily this week. NBH's founder and chief executive, Christine Pratt, who revealed civil service staff had called the helpline with bullying concerns, has agreed to resign if necessary.