The Information Commissioner's Office last night demanded the introduction of custodial sentences to punish serious breaches of the Data Protection Act, following an investigation by The Independent into the media's involvement in the trade in private information.

Writing in this newspaper, David Smith, the ICO's deputy commissioner, said: "We want action. The legislation for custodial sentences is already in place, ministers just have to bring it into force. This isn't just a crime that affects celebrities; it can devastate ordinary people's lives. It's about time we had an effective deterrent."

The lead investigator for the ICO, a former police detective inspector, told this paper that the ICO was "frightened" of investigating media organisations, claiming he had not been allowed to interview journalists who had commissioned searches from the private eyes.

Last night Keith Vaz, chairman of the Home Affairs Select Committee, said he would be writing to the Information Commissioner's office asking him to explain the "failings" of Operation Motorman in the light of The Independent's revelations. "I am concerned by the thoroughness of the investigations into both phone hacking and the use of private investigators (such as Motorman)," he said. "I will be writing to the Information Commissioner's office asking him to explain the failings in Operation Motorman. Just as we seek to revisit the regulation for the media, we should also consider more comprehensive regulation for private investigators."

Among the victims of tragedy targeted by Whittamore on behalf of newspapers was Terence Lubbock, whose son Stuart, 31, was found dead in 2001 in a swimming pool at the home of comedian Michael Barrymore. The private eye carried out three searches into ex-directory numbers of Stuart's relatives. Last night Mr Lubbock said: "I have known for some time that it's almost certain that my phone and ? more important ? Stuart's phone and other family members was targeted." He described a private eye targeting his son for a newspaper as "the lowest of the low" but, despite the new evidence of press intrusion, said: "I still have more faith in good investigative journalism than I do in the police getting to the truth or finding my son's killer."

Sara Payne, whose daughter Sarah was murdered in 2000, described the revelation that her family was targeted by Whittamore as "devastating".

Yesterday Lord Justice Leveson announced the individuals and organisations given special evidential and inquisitorial roles in his inquiry. He named 46 individuals as "core participants" in the first stage of his inquiry, which will examine relations between the press and the public. Among the list of celebrities, politicians, sportsmen and victims of phone hacking (see below) are JK Rowling, and Kate and Gerry McCann, parents of Madeleine McCann. News International and three other media groups were also granted core status.

Last night, the Culture Secretary, Jeremy Hunt, set out proposals for a regulator for media companies across all platforms. In a speech in London, Lionel Barber, the editor of the Financial Times, suggested a new Media Standards Commission, to which political bloggers and online publishers should be expected to sign up.

JK Rowling among 'core participants' in hacking inquiry

The famously private Harry Potter author JK Rowling was yesterday named among the 'core participants' expected to give evidence to the Leveson Inquiry.

There are 46 core participants in all ? and all believe their phones were hacked. They include: Chris Bryant MP, Tessa Jowell MP, Denis MacShane MP, Joan Smith, Christopher Shipman, Tom Rowland, Mark Lewis, Max Mosley, Mark Thomson, Brian Paddick, Ben Jackson, Christopher Jefferies, Paul Gascoigne, David Mills, Ciara Parkes, Simon Hughes MP, Max Clifford, Sky Andrew, Ulrika Jonsson, Mark Oaten, Michele Milburn, Abi Titmuss, Calum Best, Claire Ward, Mary-Ellen Field, Garry Flitcroft, Ian Hurst, Shobna Gulati, Mike Hollingsworth, Kieron Fallon, Ashvini Sharma, Tim Blackstone, Valentina Semenenko, Gemma Dowler, Sheryl Gascoigne, Graham Shear, James Watson and Margaret Watson.