Hospitals are risking a repeat of the Mid Staffs care scandal by ignoring patients' complaints, fobbing some off with inadequate explanations of errors and even lying about mistakes, the NHS's ombudsman has warned.

Dame Julie Mellor has accused the boards of hospitals of adding to patients' pain and letting poor care continue unchallenged by doing too little to spot and stop serious failings.

In an interview with the Guardian, Mellor voiced alarm that problems at Mid Staffs – where the hospital trust's leadership were found to have been "blind" to emerging concerns that should have triggered alarm, but that they did not take seriously – may still be happening at other hospitals. Too many boards did not give complaints enough weight and were "defensive" about alleged failings of care when they should instead be demanding answers and changes to medical practice where necessary.

"We believe that there must be a problem in the way that many hospital boards are looking at complaints, or are even not looking at them at all," Mellor said. "This means they are not learning from their patients' experience to prevent mistakes from happening again. Sadly, the Mid Staffs board's failure to listen sufficiently to patients and learn from their complaints is not exceptional."

In his report in February into Mid Staffs, Robert Francis QC said the trust's board bore much of the blame for the poor care that contributed to an estimated 400 to 1,200 deaths between 2005 and 2009. "The board lacked an awareness of the reality of care being provided to patients" and did not respond to "warning signs indicating poor care" because it gave complaints too little weight, he said.

In a new report that outlines a host of failings in the NHS complaints system, Mellor demands boards play a significant role in tackling "systemic problems in hospitals" by ensuring they provide proper scrutiny of the culture and performance and making sure they know much more about what is causing concern to patients.

"Not all hospital boards are taking complaints seriously enough and some adopt a defensive response when confronted with service failures. We see example after example of cases where hospitals aren't using complaints as the vital source of feedback they are," she says.

Too often, information about patients' concerns never reaches the hospital board, so action is not taken. Board members may have too much paperwork to read before meetings, added Mellor.

Widespread criticism of the NHS complaints system, including from bodies such as the Commons health select committee and the Patients Association, prompted David Cameron to ask Labour MP Ann Clwyd to undertake a review in the wake of Mid Staffs. Complaints to the ombudsman about the NHS in England have risen sharply from 4,257 in 2007-08 to 14,615 in 2011-12.

Mellor said boards must be ultimately responsible for how complaints are handled and must do more to ensure they are dealt with quickly, fairly and truthfully because they "set the tone" for how the hospital operates. "We know from individual cases that organisations lie to us sometimes and that's not good governance. We have had cases of [medical] records being altered."

David Behan, chief executive of the Care Quality Commission, the NHS regulator, backed Mellor. A tougher inspection regime this year will place greater emphasis on boards responding effectively to complaints, he said.

Mike Farrar, chief executive of the NHS Confederation, which represents hospitals, declined to say if he agreed that hospitals were ignoring patients' complaints. "It is absolutely right for the ombudsman to point out her concerns, and for the NHS to respond swiftly and positively to them. The NHS has indicated it is determined to step up to the challenges posed by the Mid Staffordshire inquiry," he said. Trust medical directors should give a detailed report to every board meeting about complaints, any threat to patient safety classed as a serious untoward incident should always be discussed by the board and patients who have had a bad experience should be invited to tell the board what happened to them, Mellor suggested.

Jeremy Hunt, the health secretary, backed Mellor's call for boards to be more pro-active. "Complaints can be the earliest symptom of a problem within an organisation and the NHS should use them to learn from and improve their service. Hospital boards must listen to complaints and act on them – there's no excuse not to."