Consumers are increasingly using social media websites such as Facebook to vent their anger after receiving poor service, according to a survey.
A quarter of consumers polled by the Office of Fair Trading (OFT) said that they did not get good service from businesses.
More than 80% said that they would tell their family and friends if they received excellent or poor service.
But a third said they would write a negative view on the company's website.
The OFT is encouraging companies to use its approval badge.
Some 14,000 UK businesses have OFT Approved Code status which means they provide an accessible and robust complaints procedure.
Charles Wallace, from the OFT, said: "Consumers clearly expect good standards of service and for many people it is an important part of the buying process."