Trade Secretary Patricia Hewitt has dashed supermarket group Morrisons' hopes that its bid for Safeway would escape referral to the Competition Commission.
Hewitt is referring all the potential bidders, with the exception of tycoon Philip Green, to the Commission.
As recently as Tuesday, Morrisons joint managing director Bob Stott was optimistic Morrisons' bid would not be referred.
Hewitt said: 'The deputy director general of fair trading advised that in the cases of Tesco, Sainsbury's and Asda, there is a significant prospect that these mergers may be expected to result in a substatial lessening of competition. There are reasonable grounds for believing there will be the same outcome in the case of Morrisons.'
Morrisons posted full-year sales of£4.6 billion - up 9.5 per cent on last year and like-for-like sales ahead by 5.3 per cent. Pre-tax profits rose 13.8 per cent to£276.6 million.