Shemiras Halashon Halachos
Hilchos Lashon Hara, chapter 1, section 5 Regarding speaking lashon hara, it makes no difference whether the person spoke of his own volition, or if his fellow persuaded him to speak until he spoke. It is forbidden in every case. Even if his father or rav whom he is obligated to fear asked him to tell them something, and he knows that lashon hara is included in it or even the dust of lashon hara, he may not obey them.
Hilchos Lashon Hara, chapter 1, section 6 Even if he sees that not speaking negatively against a Jew or other forbidden speech will cause a great loss in his livelihood, nonetheless, he many not speak lashon hara. For example, if the people employing him lack fear of heaven and will fire him if he is not a baal lashon hara as they are, and through this he will have no livelihood for his household, nonetheless, it is forbidden just like all other negative commands where one is obligated to give all he has in order not to transgress them.