Bradford supermarket chain Morrisons' bid for Safeway would provide "a good geographical fit" according to union bosses.
Brian Revell, T&G national organiser for food and agriculture, said he understood the benefits of a Morrisons deal but felt one of the larger companies would prevail - and that could cause fears.
He was speaking as the heads of the major supermarket chains - including Sir Ken Morrison, pictured, - outlined their cases to the Competition Commission on why they should buy Safeway.
Morrisons are battling with Asda, Sainsbury and Tesco for the store. A bid by entrepreneur Philip Green has not been referred to the Competition Commission.
Mr Revell told the Commission: "Our members within the agricultural industry are particularly anxious about greater consolidation within the sector," said
But he said his members would prefer a situation "where Sains-bury's was given the go ahead to grow its business by a part or total acquisition of the Safeway business."
Meanwhile, Peter Riley, real food campaigner at Friends of the Earth, said any takeover would lead to problems for other traders.
"Allowing Safeway to be taken over by a rival supermarket chain would be very bad for consumers, farmers and small shop owners," he said. "It will mean that powerful and rich corporations will cream off yet more trade and profits from smaller companies."
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