Half of workers stay silent about any misconduct they witness amid an "uncoordinated" approach to whistleblowing, it has been warned.
Labour MP Margaret Hodge, who chairs the Public Accounts Committee, said ministers should do more to support people who were trying to protect taxpayers' money.
She was responding to a National Audit Office report which found there was no strategic cross-government lead on whistleblowing.
Some departments may not attach the same importance to whistleblowing arrangements, while there was scope to improve internal audits, said the report.
A study of government departments covering education, health, work and pensions and defence as well as HM Revenue and Customs, found they were effective at promoting internal routes to blow the whistle, but ways for staff to raise concerns externally were less clear.
Ms Hodge said: " You only have to look at my committee's work on everything from GP out of hours services to tax avoidance to see how vital whistleblowers are to protecting taxpayers' money.
"It is extremely worrying therefore that half of workers stay silent about misconduct, possibly because they fear what will happen if they speak out. Government must do more to support those workers that try to protect taxpayers' money.
"Government's uncoordinated, piece-meal approach to whistleblowing is simply not good enough and it is completely unacceptable that almost two-thirds of those who speak out receive no response at all from their management.
"The longer this goes on, the more likely it is that patterns of wrong-doing will be missed - undoubtedly resulting in taxpayers' money being mis-spent or even lives being put at risk."