Mr Murdoch was speaking to a room full of Sun newspaper journalists who had been arrested over claims they had paid public officials, including police officers, for information.
He told staff he would do everything in his power to give them total support, even if they were convicted.
I did not intend to suggest that any violations of the law are tolerable or acceptable.Rupert Murdoch
In his letter to Keith Vaz, dated 17 July, Mr Murdoch said that he felt it was right to hear from his staff and express “personal understanding for them” at a difficult time. He said he had been reminded that some employees and their families had attempted suicide or become ill as a result of the investigation.
But the media tycoon added: “I did not intend to suggest that any violations of the law are tolerable or acceptable…”
Mr Murdoch claims that the company has assembled 23 million electronic documents for review, disclosed over 500,000 documents after 185,000 man hours of work at a cost in excess of £65m.
He said given the level of cooperation, no one who works for the company could believe that they “tolerate or accept violations of the law”.
Mr Murdoch said his language in the taped recording was inappropriate, but he was bullish about his criticism of the police: “I accept that I used the wrong adjectives to voice my frustration over the course of the police investigation.”
He added: “I am in no position to judge the competence of the investigation and should never have done so. My own lay view is that it has been more than thorough, indeed it has in some respects appeared to be excessive.
“I cannot endorse the judgement that the investigation has ‘progressed’ very well, not when some of our employees were arrested early in the investigation in 2012 and they and their families are still in limbo awaiting charge decisions.”