The T&S deal got the go-ahead from the OFT after it ruled that convenience stores were a separate market to supermarkets (a reason why some industry watchers believe Tesco could consider swooping on smaller Safeway stores).
But the OFT will not define the market it will be using to judge the bids."We will look at all the bids and give our advice to the DTI and we won't comment on market definition until then," said a spokesman.
It aims to take 45 working days to study the bids, but says because of the number involved, this could take longer. It would be up to the OFT to refer a merger inquiry.
With an acceptable offer for store disposal, the OFT could clear a deal. But the Sainsbury and Wal-Mart offers are likely to be referred to the Competition Commission which could take four to six months to decide.
Secretary of state for trade and industry Patricia Hewitt can overrule the Commission if it rejects the bids, but not if they are cleared. The new Enterprise Act, which comes into force in the summer, gives the Commission stronger powers, but for any prospective supermarket merger inquiry, she still has the final say.
If it goes that far, the Commission might recommend disposals postcode by postcode. Its industry report in 2000 focused on the UK's 120 postcode regions ­ on the basis most shoppers travel no more than 10 minutes in urban areas and 15 minutes in non-urban areas. It recommended if any of the big five want to buy or build a store bigger than 11,000sq ft within a 15-minute drive of one of its existing stores, it should need OFT consent.