The merger has created a single business with a turnover of £9.4bn, 87,500 staff and 2,249 food stores and brings together the UK's number one and number two co-op societies.
United co-op chief executive Peter Marks, who becomes CEO of the enlarged society, has said the merger will rejuvenate the co-operative movement, promising higher profits on the back of increased market share, better stores, better value and better service.
“Our immediate priority from merger will be to successfully integrate the businesses and support functions of both societies and deliver commercial synergies, so that we have one business in one year,” said Marks.
“We are fortunate that both societies are committed to broadly the same business strategy in each of the markets they operate in, so we are not talking about major upheaval and change. We will be building on the work already underway by improving and extending our store portfolio, continually improving our customer offer and, for the first time, driving real competitive advantage from the great work that has been done to unite the co-operative brand and engage with our customer members,” he added.