Investigator: I was barred from taking on the press

Information Commission feared newspapers were too big to confront despite evidence of malpractice

The agency responsible for protecting data privacy declined to prosecute journalists despite evidence uncovered by its senior investigator that an archive of illegally-obtained information belonging to a private investigator was used by several national newspapers, the Leveson Inquiry heard yesterday.

Files removed from the Hampshire office of Steve Whittamore during a raid in March 2003 could have led to an early exposé of phone hacking.

The investigator at the Information Commissioner's Office (ICO), Alec Owens, told Lord Leveson that, although he had gathered enough evidence to prosecute up to 20 journalists, he was told by his superiors to drop it.

Mr Owens said the ICO's deputy, Francis Aldhouse, told him "We can't take them [the newspapers] on, they're too big for us." The ICO's head, Richard Thomas, agreed. Mr Owens told the inquiry Mr Whittamore's files contained 17,500 "jobs" for newspapers to obtain information including ex-directory numbers and vehicle registrations.

The evidence, said Mr Owens, was "strong enough on its own to prosecute journalists – some used Whittamore 300 or 400 times".

Alastair Campbell earlier told the inquiry that he had believed Cherie Blair's former style guru Carole Caplin was the source of leaks that revealed some of the secrets of the Blairs' life inside No 10. However, Tony Blair's former spinner-in-chief revealed Ms Caplin was recently told by Scotland Yard that her mobile was targeted by Glenn Mulcaire, the jailed private detective commissioned by the News of the World.

In further revelations, Mr Campbell said police had told about invoices that had been found which suggested the newspaper where he had once been the political editor, the Daily Mirror, had paid a private investigator to look at him, his family and the former Labour cabinet minister Peter Mandelson.

Avoiding difficult questioning of his own controversial relationship with the media during the Blair years, he claimed much of the British press were in the "last, last, last chance saloon".

The solicitor behind much of the legal action that helped expose phone hacking at the NOTW told how he believed Rupert Murdoch's UK empire "sought to destroy my life and very nearly did". Mark Lewis described how the Murdoch company had ordered surveillance of him and his family. He said he had recently been shown a video of his 14-year-old daughter who had been followed at the behest of News International. The inquiry was also told of a dossier compiled by Julian Pike, a solicitor from the firm Farrar who then had NI as a client. The 2010 dossier contained information about the relationship between Mr Lewis and another solicitor involved in the Gordon Taylor case, Charlotte Harris. He said Mr Pike, and NI's former legal manager, Tom Crone, "had set out to destroy my life" because of his role in representing clients who challenged the Murdoch-owned papers.

Meanwhile, the prominent Northern Ireland MP Ian Paisley Jr has claimed his mobile telephone was hacked when he was a junior minister in Belfast, calling on the Leveson Inquiry to investigate. The North Antrim Democratic Unionist MP said he was "utterly convinced" that his phone was hacked in 2008 when he was involved in planning-permission controversies which led to his ministerial resignation.

He said: "I was so convinced that I wrote to the Metropolitan Police. I know they've conducted some preliminary investigations but so far have not found anything." He called on the Leveson Inquiry to take evidence in Northern Ireland. His claim follows the revelation that a computer used by the former minister Peter Hain may have been hacked while he was Northern Ireland Secretary.

Under fire: Guido Fawkes

The political blogger Paul Staines, who writes under the name Guido Fawkes, says he has been threatened with jail in a dispute with the Leveson Inquiry over the source of Alastair Campbell's leaked testimony, which he published online last week.

Mr Staines suggested the former spin-doctor was himself ultimately responsible for the leak, after passing a draft to trusted journalists, and that he (Staines) will refuse to name any middleman.

Lecturer given bail following hacking arrest

A university lecturer in journalism who worked for the News of the World has been arrested and questioned over phone hacking.

Bethany Usher, 31, who worked at the now-defunct Sunday tabloid and its former rival The People, was arrested at dawn on suspicion of conspiracy to intercept voicemail messages. She was later bailed until March. Ms Usher, who was young journalist of the year in 2003, was arrested, but not charged, in 2006 after trying to obtain a housekeeping job at Buckingham Palace while at the NOTW.

The lecturer at Teesside University became the 17th person questioned as part of Operation Weeting, the Met investigation into phone hacking. Ms Usher has referred several times to the Leveson Inquiry on Twitter. On Tuesday, she wrote: "Am I the only former tabloid reporter who followed the PCC [code]? Hey kids. They the rules, stick to them."

Adam Sherwin