Require collateral to enter or advance in the bureaucracy.
Serving the people isnt just a job for our committed public servants, but a promise and a commitment to the doctrine of trust and loyalty. Everyone who wants to join this wonderful institution needs to offer some asset as collateral in return for their service and loyalty to their branch of the government.
Externally - "every member of the government has given the deed to their house as collateral in case they cheat or steal from us, I wouldnt steal in this case so our government is obviously very virtuous!"
Practically - whistle blowing is disloyalty to your boss, so any jealous employee trying to smear their boss for selfish reasons obviously will lose their collateral. This should be made very clear on orientation. They'll die homeless and hungry if they cast the government in a bad light, and it will only embarrass their boss or bosses boss at most.
Advancing in the bureaucracy requires more collateral, if you have no more wealth, you need to createshare a family secret, something worth blackmailing you over (eg a signed letter of you expressing homosexual desires (assuming homophobic society), or confessingthat your brother confessed to cheating on yourhis partner, true or not, or a detailed account of how youyour father swindled huge wealth from the masses. Anything embarrassing. Confessions implicating family are needed every 3rd levelMake it up if you need to.) and give that as collateral. It's needed for any promotion. It's to ensure your loyal to your government.
Each promotion requires new information more scandalous than the last.
By the time you get to the upper rungs of the corruption, you've signed letters stating your spouse is kidnapping and eating children, you'veyou father burnt down churches, and your children were gifts from satan. Your superiors have so much dirt on you they could get your former friends to burn youyour entire family at the stake. Any allegations of corruption by a whistleblower can be met with enough evidence to brutality destroy anythe families reputation enough to dismiss or bury the allegations.
So long as the masses are fed and sheltered and entertained - you could take everything else of value for yourselves.