By Alex Kirby
BBC News Online environment correspondent
For supporters and opponents alike of the growing of genetically-modified crops, the latest advice to the UK Government will have shed little light.
Maize might benefit wildlife, Acre says
The Advisory Committee on Releases to the Environment (Acre) says some crops can be grown, while others should not.
But its recommendations are so hedged with qualifications that the ultimate decision still seems hardly any closer.
The government has won the backing for one crop of its wildlife advisers, who say several conditions must be met.
Acre, an independent advisory body, reviewed the results of the field trials, or farm-scale evaluations (FSEs) of three GM herbicide-tolerant crops.
The results, published last October, said beet and oilseed rape damaged wildlife by comparison with conventionally-grown crops, while maize did not.
Acre's review confirms these conclusions, and the result, according to its deputy chairman, Professor Jules Pretty, is "neither a green light nor a death knell for GMs".
He said: "What we're saying is 'yes, but' to GM maize, and 'no, but' to beet and rape - and the 'buts' are very important."
Acre says maize could be planted commercially provided it is grown and managed as it was in the FSEs.
A further condition is a requirement for an investigation into the withdrawal from use in 2006 of atrazine, a virulent herbicide used on the conventional control crops of maize in the FSEs, but not on the GM crop.
Acre rejects the growing of beet and rape in the same way as in the FSEs because it "would result in adverse effects on arable weed populations", an important food source for farmland wildlife.
Not long to wait
But it leaves the door open to their ultimate commercial use, saying: "There may be viable mitigation measures that could be used by farmers to offset any adverse effects".
Acre has sent its advice to ministers, who will now decide whether these three crops can be planted in the UK.
In principle the first plantings could happen in a few months, though any decision to go ahead might prove short-lived.
From the time of approval until the expiry of permission to use atrazine could be only 18 months, and once it is withdrawn the perceived environmental benefit of GM maize might disappear, if conventional crops are treated with something more benign.
Oilseed rape and beet get the thumbs down - for now
Professor Chris Pollock, Acre's chairman, told BBC News Online: "Speaking as an agriculturalist, not for Acre, I'm sure it's possible to grow GM maize under the conditions achieved in the FSEs.
All to play for
"I think some farmers may want to try a bit. In the end, it's the market that will decide this."
Acre has hardly given GM crops a ringing endorsement - its verdict seems more a recognition that some may be useful in some circumstances. Ministers still have to take a fateful decision.
It insists its advice is based on a case-by-case approach, which acknowledges the wider questions that need asking about environmental protection in farming.
The government does however have the backing of an influential authority on the issue, its wildlife adviser English Nature.
The Department for Environment, Food and Rural Affairs (Defra) said: "English Nature have advised that... GMHT (herbicide-tolerant) oilseed rape and beet should not be commercialised, but that GMHT maize may be commercialised subject to certain conditions."