Efforts to encourage whistle-blowers to expose abuse, neglect and poor care in the NHS are falling on deaf ears, a survey has found.

In October, the Government announced changes to the NHS constitution to ensure staff who raised concerns about patients' care would be protected. The changes also made it clear it was the duty of NHS staff to report bad practice or mistreatment. But a survey of 3,000 members of the Royal College of Nursing, published today, found nurses were more reluctant to report concerns and managers were less likely to act on them than in a similar survey conducted two years ago.

More than 80 per cent of those who responded said they had raised concerns about staffing levels or similar issues affecting patient safety but in almost half of cases no action was taken.

More than a third of nurses said they had been discouraged from complaining (up from a fifth in 2009) and only a third felt confident their employers would protect them (down from almost half).

The survey comes as the inquiry into the Mid-Staffordshire NHS trust, where staff failed to raise the alarm over appalling standards of care which led to up to 1,200 excess deaths, concluded its public hearings last week. The report, expected to expose a culture of bullying in the NHS as well as failures in regulators, is due to be published next year.

Peter Carter, chief executive of the RCN, said: "It is extremely worrying that nurses are being explicitly told not to raise concerns – after all we have learnt about the consequences when problems are not tackled. Cases such as the terrible situation that arose at Stafford hospital should be adequate warning about the consequences of slashing staffing levels and ignoring staff concerns."

The survey shows increased awareness of the laws around whistle-blowing but the RCN said it was concerned that problems over staffing had "widened the gulf between rhetoric and reality" over protecting those who spoke up.

Almost half of nurses were unaware they could raise concerns with organisations such as the Care Quality Commission and only 42 per cent knew they were protected by the law.

Dr Carter said: "This is yet more evidence that nurses have genuine concerns that they will be victimised if they speak up. All too often, they're right."