With revenues of £13.7bn and a pre-tax profit of more than £414m, the Manchester retail and banking giant was comfortably clear of second place engineering giant AMEC.
The Co-op's results for the 12 months to 1 January 2011 marked another record year for the group and, in the words of chief executive Peter Marks (pictured), capped a "truly remarkable and exhilarating" three-year period that included deals for Somerfield and Britannia.
And although the company has since reported a 10 per cent drop in underlying operating profits to £275.1m for the six months to July 2011, it remains committed to its bullish expansion plan.
In December 2011, the Co-op was named preferred bidder for the 632 high street branches Lloyds Banking Group is being forced to offload, while in August the Competition Commission formerly cleared its travel joint venture with Thomas Cook.
Speaking to Insider, Marks said: "We’ve had four years of exceptional growth both on top line and bottom line. This year we'll take a slight step back and our profitability will be less than last year, although ahead of the year before.
"There’s the issue of personal pride here, of course," he added. "No chief executive wants to see profits going backwards. But you have to be realistic; we are living in unique times."
Despite the tough consumer backdrop, Marks said the group "can't stop" its expansion plan. "I have very strong views about this," he said.
"We challenge ourselves and ask if we are stretching too far – but this business is playing catch up; and our competitors in their boardrooms are not sitting around saying 'lets give the Co-op a couple of years to catch up'. The world moves on."
He added: "But we are disciplined in what we do and think very carefully. I've got a very strong board who challenge me all the time about things we are doing. Don't forget, we are not used to all this change as an organisation."
Although the Co-op is a non-mover at the top of Insider's Top 500, Knutsford-registered AMEC has moved up one place to number two in the rankings. Warrington-based European Metal Recycling also moved up one to three, while United Utilities slipped from two to four. Marlowe Holdings, which trades as Edmundson Electrical, was fifth.
Insider's Top 500 ranking has been obtained by measuring the performance of companies by a combination of their turnover and profitability. First, the top 1,000 companies were ranked by turnover and then the same 1,000 were ranked again by pre-tax profit.
The two rankings were averaged and the Top 500 were drawn in order from that list. To separate those companies that finished on the same average, the one with greater pre-tax profit took precedence.
The interview with Peter Marks and the full list of Insider's Top 500 companies is in the January 2012 issue of North West Business Insider. A fuller version of the Top 500 list is also available on CD by calling Lewis Charlesworth on 0161 907 9730.