The Facebook group has about 3,000 members
Staff at shops owned by the Dixons Stores Group have been caught insulting customers on a social networking site.
An unofficial group, set up on Facebook for staff of DSG, featured comments from existing and former staff of the electronics retailer.
The comments branded customers "stupid" and recounted unflattering shop floor conversations with them.
DSG said it was "disappointed" that the comments had been left and said it would be investigating.
The Facebook group called "DSGi Employees" says it is one for "people who work/have worked for the same company". The Facebook group has about 3,000 members.
In it staff, many of whom used their real name, post comments about encounters with members of the public, many of which heap insults on them. Among many different insults, customers are called "stupid".
One member of staff at a store asked if it would be acceptable to use a cattle prod on customers who prove difficult to satisfy.
In a statement DSGi said: "We have clear guidelines for staff and will investigate any alleged abuse of customers.
"Delivering excellent customer service is at the forefront of everything we do, and so we are very disappointed that a small number of our colleagues have made these comments on a social-networking website."
It added: "We will take the necessary action with any staff found to be acting inappropriately."
Following exposure of the Facebook group, one of the administrators wrote in a comment: "Just want to say thanks to all the understanding customers out there who make our lives easier, please continue to shop with us."
In the UK, DSGi is the parent company for high street electronics retailers such as PC World and Currys.