James Murdoch has denied misleading parliament but admitted he accepts his "share of responsibility" for not "uncovering wrongdoing sooner" at News International.
The former News International executive chairman, in a letter to MPs on the culture media and sport committee said: "It has been suggested that my design to resign my role at News International reflected past knowledge of voicemail interception or other alleged criminal wrongdoing at News International. This is untrue."
He also expresses his regret over phone hacking, but says "I did not know about, nor did I try to hide, wrongdoing."
Murdoch went on: "Clearly with the benefit of hindsight, I acknowledge that wrongdoing should have been uncovered earlier.
"I could have asked more questions, requested more documents and taken a more challenging and sceptical view of what I was told, and I will do so in the future.
"I have sought to explain, however, that it was reasonable for me to rely on my senior executives to inform me of what I needed to know. In this case, the approach fell short.
"But it is important to know that I did not turn a blind eye. I was given very strong assurances about investigations recently done, and these assurances were echoed by the Metropolitan Police."
Hacked Off's Martin Moore tweeted the apology was like his father's.
Moments after the letter was punished it was announced a 51-year-old had been arrested on suspicion of intimidating a witness" by detectives investigating phone hacking.
The suspect "was arrested on suspicion of intimidation of a witness (contrary to Section 51 of the Criminal Justice and Public Order Act 1994) and encouraging or assisting an offence (contrary to Section 46 of the Serious Crime Act 2007)", Met police said in a statement.