A spokesman said it would not take part in the government-inspired debate, but instead would conduct 2,000 telephone interviews in July, drawing customer details from Co-operative Bank databases.
It will also canvas opinion through regional committees and in local debates.
A decision on maintaining the Co-op's ban on GM food and the Co-operative Bank's policy of not investing in bio-tech companies would be informed by "both our customers and the government", said the spokesman.
"We took our position on genetically modified foods a few years ago. However, there may have been a change in members' attitudes since then.
"We are a consumer-owned organisation. It is right and proper that we consult our members and raise an internal debate."
The group will release a report in the autumn which will form the basis of its GM policy in the future.