By Rebecca Harrison JOHANNESBURG (Reuters) - South Africa's Competition Commission is investigating major supermarkets over possible antitrust breaches, hitting retail stocks and raising concern about more aggressive regulation under the new government. The commission said in a statement on Monday it was investigating Pick 'n Pay, Shoprite, Massmart, Woolworths and Spar over concerns about possible anti-competitive behaviour. Shares in Pick 'n Pay slid 1.8 percent after the news. Massmart dipped 0.24 percent, Woolworths edged up 0.40 percent, Spar dropped 2 percent and Shoprite, widely seen as the cheapest grocer in South Africa, rose 0.57 percent. The JSE food and drug retailers index fell 0.43 percent and the general retail index slipped a fraction compared with a slightly firmer All-share index. One economist said the move was not only important for food prices -- a key driver of inflation in Africa's biggest economy -- but could also signal a more aggressive approach to regulation by the new government. "We may be seeing signs of a more activist government in South Africa. The implication of this runs deeper than 'just food prices' -- it may be seen as a landmark in terms of the approach of the authorities to regulating business" said Razia Khan, head of research for Africa at Standard Chartered. Investors have been scrutinising President Jacob Zuma, who's ANC won an April election, to see if there is any basis to concerns he will bow to pressure from union allies and steer economic policy to the left. The Competition Commission is independent, but some investors worry the government could exert pressure through antitrust authorities to promote its pro-poor agenda and possibly influence the outcome of corporate mergers. Food inflation has remained persistently high in South Africa despite falling international prices, and consumer groups have repeatedly called for an investigation. The authority said it would decide after the probe whether to refer the supermarket chains for hearings to the Competition Tribunal, which has the final say on antitrust issues. "This complaint initiation now aims to uncover if there are any possible competition concerns arising in the retail space, where consumers would most directly be impacted," Commissioner Shan Ramburuth said in a statement. The Commission said its concerns included the concentration of buyer power which made it difficult for small producers to get products on supermarket shelves, and long-term exclusive property lease agreements. It was also concerned supermarket groups are exchanging price sensitive information, which could hurt competition. | 
