This week's announcement confirms several months of speculation that the two accounts would be run out of the Manchester shop.
The expectation was reinforced in May, when BDH produced a TV ad promoting the fact that thousands of prices in Safeway outlets were being reduced in line with those at Morrisons stores.
The move ends Clemmow Hornby Inge's tenure of the £3 million Safeway account, leaving it clear to take on the rival Waitrose business.
Michael Bates, the marketing services director at Morrisons, said: "We've enjoyed a great partnership with BDH since it came on board last year. It is creative, it understands the sector and offers valuable strategic insight. This has translated into some very successful campaigns."
Some of the larger Safeway outlets will be rebranded as Morrisons. The Safeway name will be used for high-street convenience stores.