The chairman of the Press Complaints Commission, Baroness Peta Buscombe, has said there are “serious questions which need answers” by News International after “their own internal inquiries were not robust”.

In a letter to a lawyer who successfully sued her for libel in relation to the phone-hacking investigation, the chairman condemns all those at the News of the World who have been involved in hacking.

The chairman yesterday wrote to Mark Lewis, a lawyer for some of the celebrities and public figures who believe they are victims of hacking, stating that the committee set up by the PCC to review phone hacking is robust.

Giving evidence to the Culture, Media and Sport committee last year, Lewis said he was told by DS Mark Maberly, a Metropolitan police officer, that 6,000 people may have had their phones hacked by the News of the World.

Buscombe later said in a speech at the Society of Editors conference that Lewis had misquoted Maberly, prompting the libel claim which saw the chairman publicly apologise in the High Court and pay damages to Lewis.

Lewis, of  Taylor Hampton Solicitors, wrote to Baroness Buscombe earlier this week and she has now responded.

“Let me be clear about my position on phone hacking, which has been consistent throughout.

“It is a deplorable practice, and an unjustifiable intrusion into an individual’s privacy,” she said in the letter.

“The commission has always said that it is a breach of the Editors’ Code.

“As I said to the Independent in February this year, it brings shame upon the whole journalistic profession. I condemn all those at the News of the World who have been involved in it.”