Protesters have ripped up some GM crop trials
Eight of the field-scale trials will be held in Norfolk, six in Lincolnshire, five in Gloucestershire, four in East Yorkshire, three in Shropshire, three in Dorset, two in Durham, and two in Aberdeenshire.
The others will take place in Fife, Cumbria, North Yorkshire, Cambridgeshire, Suffolk, Nottinghamshire, Leicestershire, Worcestershire, Warwickshire, Hertfordshire and Sunderland in Wearside.
Defra will announce the proposed locations for maize, which is sown slightly later, in the week beginning 11 March.
The trials were designed to detect unacceptable effects on the environment, it said in a statement.
"All the seeds have been through years of rigorous safety tests," Defra said. And the crops will be separated from other produce to minimise any risk of cross-pollination.
But even if the results of the trials - due next year - are successful ministers may not approve the technology, despite previously insisting the decision would be based on science alone.
'Valuable' data
The sites were selected from an initial pool submitted by the Supply Chain Initiative on Modified Agricultural Crops (Scimac).
Its chairman Roger Turner said: "This independent study will provide valuable information about the comparative biodiversity effects of weed control in GM and non-GM crops.
"The results of this research programme will help ensure future decisions about GM crops and their role in British agriculture are based on sound scientific data."
But Pete Riley, GM campaigner at Friends of the Earth (FoE), said the separation distances around these GM crop trials were "pathetic".
"If they go ahead, neighbouring and organic crops within a five-kilometre (three mile) radius will be at risk from GM contamination," he said.
'Reckless
"The government knows the separation distances are inadequate but has recklessly failed to act.
Friends of the Earth pointed to a Food Standards Agency study which found that 15% of bakery products had GM soya in them, albeit at levels below the allowed level of 1%.
Although the FSA said these levels were not necessarily the result of contamination, FoE added that: "These trials may lead to similar contamination incidents in the food chain and deny the public its right to say no to GMOs."
Concerns surrounding GM technology centre on the impact on the environment, wildlife and human health.
The government has asked the Agriculture and Environment Biotechnology Commission (AEBC), the independent UK advisory body on the issue, to organise a public debate on attitudes to genetic modification.