Praise be to Allaah.
It is not permitted for a Jew to be in charge of that, and it is not permitted to leave him in that position. It is not permitted to rely upon his evaluation. The ruler, may Allaah give him strength, will be rewarded for firing him and replacing him with a trustworthy Muslim, and those who help him to do that will also be rewarded. Allaah says (interpretation of the meaning):
“O you who believe! Take not as (your) Bitaanah (advisors, consultants, protectors, helpers, friends) those outside your religion (pagans, Jews, Christians, and hypocrites) since they will not fail to do their best to corrupt you. They desire to harm you severely. Hatred has already appeared from their mouths, but what their breasts conceal is far worse. Indeed We have made plain to you the Ayaat (proofs, evidences, verses) if you understand” [Aal ‘Imraan 3:118].
The meaning of this aayah is: do not take as close advisers who will be deeply involved in your affairs and will be dealing with your secrets and important matters, people other than you, i.e., kuffaar. “They will not fail to do their best to corrupt you” means, they would not hesitate to cause harm and corruption if they are able to. “Hatred has already appeared from their mouths” means, they say, we are your enemies.
And Allaah knows best.