Recent decades have witnessed a distinct increase in the sales and popularity of private labels. The growing market share of private labels has transformed the landscape of retail competition in developed countries. Major retailers are no longer confined to their traditional roles of purchasers and distributors of branded goods. By selling their own label products within their outlet they compete with their upstream brand suppliers on sales and shelf space. This 'vertical competition' is not confined solely to 'value' categories of products. These days, retailers offer private label goods catering for the value, specialized and premium markets. These developments, and the increasing confidence that consumers have in private labels, have increased the bargaining position and market power of retailers as their labels compete directly with the leading manufacturers' brand and its 'value' alternatives. This unique relationship and the increased role played by private labels in Europe, and more specifically the United Kingdom, raises fundamental questions as to their pro-, and possible anti-, competitive effects. It further highlights the shifting power balance between the producer and distributor and between the private label and branded good. This paper focuses on the effects of private labels, sold in major supermarkets, on retail competition and consumer welfare. In particular, it considers how supermarkets may affect competition due to the fact that they retain control over shelving, in-store promotion and the pricing of branded and own label goods. Furthermore, it reviews the enforcement of European competition laws in a private label environment and the difficulty in balancing the beneficial short-term effects of private labels and their possible, harmful, long-term effects. It subsequently questions whether these difficulties imply a lack of competitive harm or reflect a gap in regulation, as traditional analysis fails to encompass the increased market power of retailers and the existence of vertical competition.