Advice to New York City employees who wish to stay employed: Do not ask a welfare recipient to watch your beloved pet ferret.

A caseworker at the city’s Human Resources Administration resigned his job after doing just that, the city’s Conflicts of Interest Board said on Tuesday, the latest episode in a long line of municipal controversy wrought by the musky yet misunderstood mammal.

The caseworker, Kempe Hope, exploited his position by soliciting a paid ferret-sitting session from a person whose benefits he was overseeing, the board found.

It was a lesson learned too late for Mr. Hope, who discovered that of all the political pests that can vex public servants, the ferret often leaves the harshest bite.