Pushing a major reform, the government today allowed 51 per cent foreign investment in the multi-brand retail, paving way for global chains like WalMart, Carrefour and Tesco to open mega stores in 53 major cities. The decision, a game-changer for the estimated USD 590 billion (Rs 29.50 lakh crore) retail market, is taken at the meeting of the Cabinet presided over by Prime Minister Manmohan Singh.