The Government has failed to do enough to protect and encourage whistleblowers to come forward, a group of MPs has warned.
In a sharp rebuke to ministers, the Commons Public Accounts Committee (PAC) said it is "disappointed by the lack of urgency shown in dealing with this important topic" and demanded more be done to drive through changes.
The comments, contained in a report published on Friday, come after whistleblowing scandals have shaken public confidence in institutions.
In a landmark review published last year, Sir Robert Francis QC said a "climate of fear" existed in the NHS in which staff who raised concerns about substandard care were bullied and victimised.
In a previous report in August 2014, the committee said whistleblowers "have been shockingly treated", and warned that attempts by departments to improve their policies had failed "in modifying a bullying culture".
Meg Hillier, who chairs the committee, said: "Whistleblowing policies are too important to get wrong and the Government should be leading by example. The fact that it isn't should concern us all.
"Whistleblowers are on the frontline of defence against wrongdoing and bad practice. They have a vital role to play in the day-to-day accountability of public spending and public service.
"This should be recognised by and enshrined in the culture of every Government department. Where it isn't, senior officials in those departments should be held properly to account."
She added: "There is little doubt that in the past potential whistleblowers will have been deterred by the shoddy treatment experienced by others. It is not beyond the scope of Government to change that, in its own workplaces and beyond."
The report attacks the "slow progress" made in ensuring that those who speak out are protected.
It states: "Nearly a year and a half has elapsed since the previous committee reported on whistleblowing, but we heard little to convince us that any real change has occurred on the ground."
It said the "Task and Finish" group, established to look at whistleblowing across Whitehall, has met only once, and the Cabinet Office does not have the data it needs to identify where improvements are needed.
While new guidance has been drawn up, the focus has been on policy "rather than instilling the positive cultures and behaviours required to support those raising a concern", it added.
Richard Bacon, vice-chairman of the committee, said tangible progress has been "far too slow".
He said: "Whistleblowers may be individuals but if whistleblowing policies are to be fully effective then they must address organisations as a whole.
"That means establishing a positive culture around whistleblowing in the workplace and ensuring all employees in that workplace feel comfortable about raising concerns."
The committee has set a June deadline for the Cabinet Office to report back on progress being made.
A Cabinet Office spokesman said: "The Government takes this issue very seriously. We have worked hard to create a culture where employees are confident to blow the whistle.
"In January, we collected data for the first time from across departments on whistleblowing cases and will continue do this on a regular basis. This information will be important as we take action to address this issue.
"As agreed with the Committee, we will respond to them by the end of the month to show the progress that we have made."
Rachael Tiffen, head of the counter-fraud centre of the Chartered Institute of Public Finance and Accountancy (Cipfa) said: "These findings are worrying. Whistleblowing policy is essential for tackling fraud and corruption.
"Since fraudsters are helping themselves to a staggering £21 billion from the public purse each year, with barely a fraction of a per cent being caught, the Government must take these recommendations seriously.
"These issues are already being challenged in local government. Cipfa is working with councils, government and the Local Government Association to develop a comprehensive approach including robust and fair whistleblowing policies."