Health regulators should warn nurses, doctors and midwives they may be investigated if they fail to report concerns about colleagues, MPs say.
The call comes from members of the cross-party health select committee.
But the MPs said NHS whistle-blowers sometimes end up facing disciplinary action themselves from employers if they do raise concerns.
The General Medical Council (GMC), which regulates doctors, said it was committed to doing more in this area.
The committee says a clear signal should be sent by the GMC and the Nursing and Midwifery Council (NMC) that staff who fail to report concerns are at as much risk for being investigated as they are from any poor practice of their own.
The committee's chairman, the Conservative MP Stephen Dorrell, said: "This is an underdeveloped part of the regulators' work.
"We regard the principle behind this wider obligation as an important safeguard for patients.
"We're not suggesting a new doctrine for staff. It's part of the professional obligation - being aware of the practices around them is in the professional codes.
"There have been examples of people raising concerns, and then facing inappropriate or heavy-handed action from their employer.
"We intend to follow up and to examine what is appropriate and what isn't, in terms of how employers respond."
The GMC is currently investigating doctors at Stafford Hospital whose own work was blameless, but who allegedly failed to report colleagues.
The GMC said that in the past five years it had investigated more than 80 doctors over allegations that they did not report, or did not report soon enough, their concerns about the risk a colleague posed.
The NMC was unable to give details of any similar investigations.
Threats and bullying
Peter Walsh, who heads the charity Action against Medical Accidents (AvMA), said: "Many whistle-blowers are affected by threats and bullying. They lack independent help and support.
"If there are doctors or nurses who unreasonably fail to report serious concerns, they should be held to account.
"However, the management who make it so difficult for staff to raise concerns must also be held to account."
The GMC's chief executive, Niall Dickson, said: "The committee rightly challenges us, as well as all health professionals, to speak up if they are aware of poor patient care.
"We know there is more we can do in this area and we are committed to doing it.
"The important point is that doctors are aware of these issues and act appropriately. We will be working with the profession to take this forward."
The Department of Health has held a consultation about strengthening safeguards for whistle-blowers.
It closed in January, with no response published yet.