The NHS is to establish a patient feedback website, styled after the popular travel site TripAdvisor, to allow patients to post complaints online – including those containing potentially derogatory comments about medical staff – and show hospitals' responses to them in real time.

In an interview with the Guardian, Tim Kelsey, the NHS director in charge of patients and information, said a low-key three-month trial involving 2o hospital trusts on the Care Connect website had seen complaints and reviews logged, mapped and dealt with, night and day, in London and the north-east. The scheme will be rolled out nationally next year.

Kelsey pointed out that serious issues had already been tackled using the system – highlighting one instance when an elderly patient recovering from a cancer operation had been "left without morphine for a few hours – something she needed every four to five minutes".

Her daughter posted on the website that "the surgeon came into the room and not only berated the staff again but said 'this unit is really going downhill'. The whole experience is surely unacceptable in this day and age."

Kelsey said that this was not about "naming and shaming" but instead allowed the NHS trust in question – St Helier in south London – to contact the patient within hours of the complaint, before escalating it to the patient liaison service within 48 hours.

"It's what any consumer of health services would expect," he said.

The news of the system's planned roll-out came as the Patients Association charity published its annual study highlighting stories from patients and their families. The report said too many parts of the NHS had "lost their way", with a lack of basic care in hospitals, and the NHS often forgetting that "care and compassion should be at the heart of what staff do".

Kelsey said that by embracing "openness" the NHS would improve. He said the idea came from the United States, where cities such as Boston, New York and Miami have pioneered a system of public feedback to reshape public services. "Local authorities have invited the public to tell them about services. People can tweet, send in pictures. In the US 90,000 citizens do this every day about their trash not being collected and the state of roads.

"This allows local authorities to hold providers of services to account and it's transforming services. The last mayor of New York, Michael Bloomberg, said that he thought it was a more legitimate form of citizen engagement than democracy itself".

The system allows the NHS to deal "intelligently" with patients, often in surprising ways, Kelsey said. "This has gone really quite well. So we have taken the decision to roll it out nationally next year"

He said this was "creating a 24/7 modern consumer health service". The NHS had to innovate in terms of patient safety, especially since the Francis inquiry into the appalling care at Mid Staffs hospital concluded that the health service must become more open and transparent and "embody a duty of candour".

While the public can access Care Connect online, by text, phone, Twitter and Facebook, their complaints and reviews are first assessed by case handlers who moderate the posts for privacy and, if out of hours, they contact the hospital to ensure the issue is taken up immediately.

However, posts on social media cannot be moderated – possibly exposing NHS staff to libel and threatening to breach patient confidentiality. "You cannot screen this stuff out on Twitter or even on Facebook which can see people repost stuff," said Phil Booth of privacy campaigners medConfidential. "I am not sure they have thought this through."

Comments on the site last night showed that at a London hospital vulnerable patients were being "smeared and laughed at" by staff; that a routine blood test left a patient with a lump the size of a tennis ball at Guy's hospital; in Essex a woman complained that she waited two months for contraception; and in Surrey an alleged failure to spot an ecotopic pregnancy left a woman infertile.

The British Medical Association had concerns that comments would be patrolled effectively.

A spokesman said: "It's important that comments that are defamatory, or which threaten the confidentiality of other patients, are screened out and consideration is given to how patients might interact with the service using social media."

Jane Barnacle, Kelsey's deputy, admitted that it was difficult to police complaints made on Twitter and Facebook. "The law does apply to social media so people would have to be careful."

The system was designed to "allow the public to choose the privacy level that suits them. If they wish to remain anonymous they can, or they can choose to have the details of their problem made public, as long as it passes the moderation process, either with or without their name published."

The website has cost £150,000 to set up. The plan is to bring in a private company eventually to run the service. The NHS deals with over 1 million patients every 36 hours, but officials are confident that it can handle the volumes of complaints.

• This article was amended on 29 November 2013. The earlier version had a mistranscription in a quote from Tim Kelsey which had him referring to people complaining "about their trash not being delivered".