US discount retailer Grocery Outlet has secured private equity investment from Berkshire Partners, it has been announced.

The California-based retailer claims it offers "extreme bargains" on branded products and has over 130 stores in the western US. The stores are run by independent operators.

"We believe Grocery Outlet has a unique operating model that offers customers tremendous values on brand names they trust in a friendly, high quality shopping environment," said Berkshire Partners MD Chris Hadley.

The private equity firm said only that it had made an "equity investment" in the business and declined to disclose financial details or the size of any shareholding.