The alliance has now sent a letter to Trade and Industry secretary Patricia Hewitt calling on her to confirm that the bids will be investigated by the Competitions Commission.
The letter says: 'We find it inconceivable that the Government would not require an investigation by the competition authorities of any merger which results in further concentration of market power among the multiple retailers.'
The alliance, which includes 19 organisations, believes any takeover could hinder smaller retailers' ability to compete, as well as customer choice.
As well as writing to the secretary of state the alliance has sent a submission to the Office of Fair Trading, which last week was seeking views relating to bids made by Morrisons, Sainsbury and Asda. A further submission is being sent this week regarding Tesco's bid.