This is despite the company reporting a pre-tax profit of Â£36m in the first half of 2015, compared with a loss of Â£9m a year earlier.
The group said the turnaround was due to "robust trading" in its food and funeral businesses.
These are the first results since radical changes to the business were brought in at the end of last year.
Following a review of the business by Lord Myners, the number of board members was cut drastically, while directors had to have qualifications suited to running the business. Members were also given one vote each.
The business recorded a deficit of Â£2.5bn in 2013 following massive losses at the Co-operative Bank. Following changes in the ownership structure of the bank, the Co-op Group now holds just a 20% stake in the bank.
"We've made a good start on the three year journey to rebuild the Co-operative Group," said chief executive Richard Pennycook of the half-year results.
"These early days are about fixing the basics - putting in place new leadership teams and providing the investment to deliver the strategies for our businesses. Our customers and members are beginning to see the difference.
The food business saw like-for-like sales at its main convenience stores increase by 3.3%, as well as 35 new store openings.
The funeral business saw volumes rise by almost 12%, "principally due to a high death rate".
Despite the improvement in the business seen in the first half of the year, the company warned that "we expect full-year profitability to reduce year on year, given the planned and increased levels of investment we are making in the second half of the year".
It also said that, again due to greater investment, it was unlikely to declare any dividends before 2018.

The city also ranks second in a list of Britain's most congested cities, while Glasgow is third.
Only London ranked worse than Scotland's largest cities in the survey of the UK's roads by Inrix Roadway Analytics.
It found that the jams could cost drivers in Scotland £5.1bn in wasted time over the next decade.
The firm studied traffic hotspots in 21 UK cities in September 2016.
It assessed the impact of the congestion by looking at the average duration of traffic jams, their average length and the number of times they occurred.
The research found that the impact of Edinburgh's 455 traffic hotspots was second only to London and was likely to cost drivers £2.8bn by 2025.
Glasgow was ranked third in the same list - worse than Birmingham, Manchester and Bristol. It's 357 hotspots could cost £2.3bn over the next 10 years, Inrix said.
Researchers calculated the time wasted by drivers in traffic jams across the UK could cost £61.8bn by 2025 if congestion levels are not reduced.
And in their survey of 123 cities across Europe, London was found to have more traffic "pinch points" than any other city.
It also ranked worst in an assessment of the impact of its traffic jams. Rome was second and Paris was third.
Inrix chief economist Graham Cookson said: "Only by identifying traffic hotspots and analysing their root causes can we effectively combat congestion."
The Co-operative Group has said increased investment means profits this year will be lower than in 2014.
[NEXT_CONCEPT]
Four of the UK's worst traffic bottlenecks occur on the Edinburgh bypass, according to new research.