Meiri(Shabbos 33b): Even though lashon harah is the foundation of a number of sins and something which our sages spend much effort in severely attacking – there are two conditions in which lashon harah is permitted 1) This is mentioned in Erchin (15b) that derogatory words which are said in the presence of the one being talked about are not considered lashon harah. The gemora questions this and says that lashon harah said in the presence of the one being criticized is surely impudence and lashon harah? This is explained with a statement of R’ Yose that he never said any words about another person and looked around to make sure the person wasn't there. In other words if the person speaking does not refrain from saying the negative words before the one he is speaking about – there is a leniency and this is not considered lashon harah. For example if the speaker directly complains about the other person or calls him a thief and others such negative statements in his presence – the speaker is not considered speaking lashon harah. That is because he wants the person he is criticizing to hear what he is saying. 2) This is also mentioned in Erchin (16a) that whatever is said in the presence of three people is not considered lashon harah. That is because the speaker is saying the negative things with the full desire that his views reach the person he is speaking about. That is because all matters that are known to three people is not considered concealed or a secret. Therefore the speaker is not considered to be saying lashon harah.