NHS boss Sir David Nicholson was warned four years ago about problems at a trust which is being investigated for persistently high death rates, a whistleblower has claimed.
Gary Walker, who was sacked in 2010 as chief executive of United Lincolnshire Hospitals Trust, said Sir David ignored him when he raised concerns about patient safety in 2009.
The trust is one of 14 being investigated by health chiefs over high mortality rates in the wake of the public inquiry report into serious failures at Mid Staffordshire NHS Foundation Trust.
Julie Bailey, who set up the campaign group Cure the NHS after her mother Bella died at Stafford Hospital in 2007, said Mr Walker's comments made Sir David's position untenable. And union Unite called for Sir David's resignation, saying he presided over a "culture of fear and bullying" in the health service.
Mr Walker, who has spoken out in defiance of a legal gag, told the Daily Mail Sir David was "not interested in patient safety" and called on him to resign. He told the newspaper: "I want David Nicholson to be held to account. I warned him that this was going to happen. I warned him that Lincolnshire was going to become the next Mid Staffordshire. He didn't investigate those concerns, and now look what's happened."
Sir David, who was chief executive of the West Midlands Strategic Health Authority between August 2005 and April 2006 - at the height of the troubles in Mid Staffordshire - and is now head of the NHS Commissioning Board, has ignored calls for his resignation.
When asked if she thought the latest development made Sir David's position untenable, Ms Bailey said: "It certainly does. It is a clear indication that David Nicholson does not take patient safety as a priority - like at Mid Staffs.
"We do not know how many people lost their lives at United Lincolnshire but there were hundreds who lost their lives at Mid Staffs because of his lack of action. This is a clear indication that the NHS is using public money to gag people who wish to raise concerns about patient safety and a clear indication that David Nicholson knew about it."
But last week, Sir David said he was "not ashamed" of being in his job following the publication of the Francis Report highlighting the "appalling and unnecessary suffering" of hundreds of patients at Mid Staffordshire between 2005 and 2009.
Mr Walker was sacked in 2010 for gross professional misconduct over alleged swearing at a meeting. He claims he was forced to quit for refusing to meet Whitehall targets for non-emergency patients and was then gagged from speaking out as part of a settlement deal.