Convenience chain Mills Group is set to open its largest-ever stores after securing five supermarkets from The Co-operative Group.

The five Somerfields stretch from Durham to Nottingham and are between 5,000 sq ft and 9,000 sq ft two to three times the size of Mills Group's existing c-stores.

The Nisa-Today's member has been steadily moving away from its CTN roots this year but the move marks the chain's first move into the supermarket sector.

"They are great supermarkets and will be the biggest stores we have once we have taken them over," said MD Nigel Mills.

The retailer would take over the stores on 1 November and would open one store a week for the next five weeks, Mills added. He estimated the acquisition would increase Mills Group's retail turnover from £58m at the beginning of the year to £90m.

The new stores would also improve the company's buying power on products such as meat, poultry and bread. The company was planning to introduce bakery, fresh produce, and meat, fish and poultry ranges comparable to Sainsbury's Local or Tesco Express across its estate by 2011. "We will be able to cascade this down into our c-stores and it will give us a competitive product range," he said.

This August, the retailer laid out an ambitious plan to double its profits to £2m and increase its turnover to £100m in the next two years following a reorganisation and rationalisation of the business.

The acquisitions mean Mills Group, which operates about 80 c-stores and CTNs in the north of England, the Midlands and South Wales, has nearly doubled the number of stores it planned to acquire this year.

In December last year, Mills said he was aiming to buy six stores in 2009 after acquiring just one store in five years. It bought a 2,500 sq ft store in Armley, Leeds, from an independent in January and secured five stores from Sainsbury's in April.