Dominic Mohan, the current editor of The Sun, told the Leveson Inquiry today that the paper could be a "powerful force for good" through its campaigns, support for charities and efforts to explain complicated stories in a clear way.
At the first session of the inquiry since Christmas Mr Mohan, a former showbusiness reporter who took over at the helm of Britain's best-selling daily paper in 2009, appealed for there to be a "level playing field" between the press and internet publications.
"I do think it could be a potentially mortal blow to the newspaper industry that's already wounded," he said.
"I think the combination of an over-regulated press with an unregulated internet is a very, very worrying thought."
Mr Mohan was asked about comments he made at an awards ceremony in 2002 in which he thanked "Vodafone's lack of security" for the showbusiness exclusives in rival paper the Daily Mirror.
The inquiry heard this was a reference to the fact that it was easy to hack into mobile phones on the Vodafone network.
But Mr Mohan insisted it was "a joke", saying: "It was a cheap shot at the Mirror because they'd had a particularly good year."
Earlier former Sun editor Kelvin MacKenzie defended his "bullish" approach to editing the paper as he acknowledged that the publication has now become "more cautious".
He told the inquiry he did not spend much time worrying about journalistic ethics or which stories would sell more copies, leaving it to his readers to decide whether his decisions were right.
Mr MacKenzie, who edited The Sun from 1981 to 1994, also insisted that Rupert Murdoch never put him under commercial pressure and in fact often felt that he went too far.
"I didn't spend too much time pondering the ethics of how a story was gained nor over-worry about whether to publish or not," he said in a witness statement.
"If we believed the story to be true and we felt Sun readers should know the facts, we published it and we left it to them to decide if we had done the right thing.
"They could decide we were correct and carry on purchasing us - in my time in ever-increasing numbers - or could decide we were wrong, in which they could decline to buy us again, ie Hillsborough."
This was a reference to The Sun's sharp circulation decline on Merseyside over its controversial coverage of the 1989 Hillsborough disaster, in which 96 Liverpool football fans died.
Mr Murdoch was furious when he found out The Sun was to pay £1 million in damages to Elton John after a story falsely claimed the singer had hired rent boys, the inquiry heard.
Mr MacKenzie recalled sending the media mogul a fax about the case then receiving a 40-minute phone call of "non-stop abuse". He told the hearing: "Let's put it this way, he wasn't pleased."
He stood by comments he made in a Leveson Inquiry seminar in October, when he said: "My view was that if it sounded right it was probably right and therefore we should lob it in."
He said he had looked up the definition of the word "lob" in an online dictionary, and found it meant "to throw in a slow arc".
"The point I'm making is that we thought about something, and then put it in," he said.
Mr MacKenzie told the hearing that when he was Sun editor he would meet then-prime minister Baroness Thatcher twice a year, and might see Cabinet ministers between six and ten times a year.
"I was always astonished that a prime minister would want to meet a tabloid journalist with one GCSE, and wondered where the equivalence was in that discussion," he said.
Mr MacKenzie has previously described the Leveson Inquiry as "ludicrous" and suggested it is only being held because of Prime Minister David Cameron's "obsessive a***-kissing" of Rupert Murdoch.
The colourful former editor was behind a number of contentious front-page Sun headlines, including "Freddie Starr Ate My Hamster" and "Gotcha", about the sinking of the Argentine warship General Belgrano during the Falklands War in May 1982.
He rejected Anne Diamond's evidence to the inquiry in November that Mr Murdoch's editors waged a vendetta against her after she asked the media tycoon how he slept at night knowing his newspapers ruined people's lives.
The former TV-am presenter spoke of her distress when The Sun published a front-page picture of her and her husband carrying the coffin of their baby son Sebastian, a victim of cot death, at his funeral in 1991.
But Mr MacKenzie told the inquiry: "I have had the advantage as distinct from Ms Diamond of working with Rupert Murdoch for 13 years closely.
"And I have never heard him say 'Go after anybody' under any circumstances, whether it is the prime minister, a failing breakfast show host, or anybody. He's never said it.
"Why she should believe that her career has suffered because of one conversation is beyond me."
Mr MacKenzie said the culture at The Sun had changed under its recent editors, and admitted he himself became "less bullish" towards the end of his time in charge.
"The editors are more cautious and were probably in a changing world right to be cautious," he said.
The session was held up shortly into Mr MacKenzie's evidence when a man shouted across the courtroom: "Ask him about Michael Stone."
Lord Justice Leveson told the man to stop or he would be asked to leave. The man replied: "Am I in contempt?" before walking out of the hearing.
The heckler identified himself as Alexander Baron, who runs a website protesting the innocence of Stone, who is serving three life sentences after being convicted of bludgeoning mother and daughter Lin and Megan Russell to death with a hammer and attempting to murder Megan's sister Josie in Chillenden, Kent, in July 1996.
Meanwhile, Gordon Smart, The Sun's showbiz editor, said he and his team were "respectful" of people's right to privacy when deciding whether to run a story.
"It's a balancing act we have to weigh up on a daily basis," he told the hearing.
"I would like to think most of the time we get it right. Occasionally we get it wrong."
Prime Minister David Cameron set up the Leveson Inquiry last July in response to claims that the News of the World commissioned a private detective to hack murdered schoolgirl Milly Dowler's phone after she disappeared in 2002.
The first part of the inquiry, sitting at the Royal Courts of Justice in London, is looking at the culture, practices and ethics of the press in general and is due to produce a report by September.
The second part, examining the extent of unlawful activities by journalists, will not begin until detectives have completed their investigation into alleged phone hacking and corrupt payments to police, and any prosecutions have been concluded.
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