Labour MP Chris Bryant, who has led the phone-hacking campaign, also described the decision to lift the suspensions on all arrested staff as the “most cynical piece of hypocrisy”.
He said News International had campaigned for public officials who have been charged with criminal offences to be suspended from office but was now not applying the same requirement to its own staff.
Bryant said: “I think it is massively premature because one would have thought the Murdoch empire would want to wait until Leveson had completed his inquiry and the police and prosecuting authorities had completed their investigations.
“He (Mr Murdoch) is meant still to be ‘draining the swamp’ and yet the swamp is meant to produce another newspaper.
“The most cynical piece of hypocrisy is that News International has tirelessly campaigned for people who have been charged to be suspended from public office and yet journalists who have been charged at News International are apparently not going to be suspended.”
During a visit to the newspaper’s headquarters in Wapping, east London, Murdoch declared his “unwavering support” for its journalists as he announced he was lifting suspensions of all arrested staff.
The media mogul said he will begin publishing the top-selling tabloid seven days a week by launching a new paper called the Sun on Sunday “very soon”.
The Sun has been rocked by the arrests of 10 current and former senior reporters and executives since November over alleged corrupt payments to public officials. There has been widespread speculation that News International would begin publishing a Sunday version of The Sun ever since the News of the World was closed last July over the phone-hacking scandal.
Murdoch is understood to have spent yesterday afternoon on the newsroom floor. He is thought to have spoken to individual journalists but not made any formal address.
Staff leaving the building were reluctant to speak to waiting journalists but the mood inside was said to be “more relaxed”.
Murdoch spoke to a number of Sun reporters on the newsroom floor, accompanied by eldest son Lachlan.
A source played down the significance of the absence of Murdoch’s younger son James, who is chairman of News International.
The source said: “James Murdoch has other commitments and is out of the country, and asked Lachlan to accompany his father.”
At the heart of anger among staff was the secretive committee set up by Murdoch to work with the police, which has handed over information after trawling through 300 million emails, expense accounts and notebooks in the hunt for signs of criminality.
Murdoch said the committee would continue to work with the police and said illegal activity would not be tolerated. However, he said those journalists who had been arrested would have their suspensions lifted and could return to work.
“I am confident we can live by these commitments and still produce great journalism,” he said. “We will build on The Sun’s proud heritage by launching The Sun on Sunday very soon.”
“Finally some good news,” one member of staff said. Another described the arrested Sun employees returning to work as “heart-warming news”.