Fair competition is permitted in Jewish law and practice. Jews basically believe in the advantages of free market, where regulations would be applied mainly to basic-needs products like food. If an item which is considered to be a basic need was overpriced above certain amount (15% - 20%) the courts (bet-din) might force the seller to reimburse a customer the extra money he has paid. Other than that, competition is allowed because lower prices and better quality will ultimately benefit the consumer.
But, is anything permitted in the name of competition?
In the business world, Lashon haRa is often spoken as a "marketing tool".
You may have observed this technique when asking a salesman for his opinion about a product and receiving, instead, a thorough denunciation of his competitor's merchandise. "Well, that's business," is often-heard as an after-the-facts rationalization.
Such reasoning is not an excuse for speaking Lashon haRa.
Maligning competitors' merchandise is an all too-common practice. The obvious motivation behind this is a desire to increase one's sales by minimizing competition.
Sometimes there is a second motivation at work: jealousy. Someone with a product to sell finds it difficult to accept the fact that a competitor has better merchandise or better prices. Speaking Lashon haRa is his attempt at convincing others of what he would like to believe — that his item is superior.
Adapted from: “Chofetz Chaim, a daily companion".
*Note: this statement should not be considered exhaustive regarding all the intricacies of Jewish law in monetary and commercial issues. It should serve only as an introduction to the concept of Lashon haRa in business.