After 52 years, mogul's ally quits to protect jewel of US empire

Within hours of Rebekah Brooks tendering her resignation as head of News International, her predecessor Les Hinton, one of Rupert Murdoch's closest lieutenants in the United States, fell on his sword, saying that the pain his reporters had inflicted on innocent people was "unimaginable".

Mr Hinton has been the publisher of The Wall Street Journal since Mr Murdoch bought it in 2007 and his continuing presence was threatening to drag the media mogul's prize US newspaper asset into the scandal.

"That I was ignorant of what apparently happened is irrelevant and in the circumstances I feel it is proper for me to resign from News Corp and apologise to those hurt by the actions of News of the World," Mr Hinton said in a resignation letter.

Mr Hinton's departure is a personal blow to Mr Murdoch. The men have known each other for 52 years, since UK-born Mr Hinton landed a job at the mogul's first newspaper in Adelaide, Australia, where his family had relocated. In a letter to staff at Dow Jones, the parent company of The Wall Street Journal, Mr Murdoch reminisced yesterday how one of the then 15-year-old Mr Hinton's first jobs was to bring him sandwiches each day. "Little did we both realise that we would be travel companions on a journey through the world of magazines, Hollywood, television studios, coupons and the greatest newspapers on the globe," Mr Murdoch said. "Little did we realise that our corporate relationship would end in these circumstances."

News Corp, with its new public-relations advisers, Edelman, has been trying to prevent the scandal from spreading to the US, where the FBI is already investigating rumours that NOTW journalists tried to hack the phones of 9/11 victims. Revelations about the unseemly side of British tabloid journalism threatened to undermine the integrity of The Wall Street Journal and Mr Hinton is expected to be called upon to give lengthy evidence to the inquiry in the UK.

It was clear last night that Edelman's strategy included clearing out executives who appear either to have covered up the hacking scandal or, at least, failed to properly investigate hacking claims.

Mr Hinton was the executive chairman of New International at the time of the 2007 internal report and gave an assurance to MPs that year that a "full, rigorous internal inquiry" had been conducted, which had left him convinced that hacking was restricted to the royal reporter, Clive Goodman. Mr Hinton pointed out the investigation would continue. The testimony to the Commons Culture, Media and Sport Select Committee was the start of what became News International's "rogue-reporter" defence that phone hacking was restricted entirely to Goodman and Mulcaire – a stance that was finally abandoned this January only when emails implicating another NOTW journalist were surrendered to Scotland Yard.

In further evidence to MPs in 2009, Mr Hinton said he remained happy that NOTW had gone to "extraordinary lengths" to uncover any additional evidence and nothing had been found. "Efforts made to discover any other wrongdoing had been conscientious and thorough," he said.

"My testimonies before the Culture Media and Sport Select Committee were given honestly," Mr Hinton said last night. "I have watched with sorrow from New York as the News of the World story has unfolded. I have seen hundreds of news reports of both actual and alleged misconduct during the time I was executive chairman of News International and responsible for the company. If others had evidence that wrongdoing went further, I was not told about it."

After working as a foreign reporter in the US for the company, Mr Hinton became an executive and was flown to the US to assume control of The Wall Street Journal.