The Swiss Federal Environment Office has backtracked on a decision denying scientists permission to conduct field trials of genetically modified wheat.
The turnaround comes a few months after Switzerland's environment minister, Moritz Leuenberger, demanded the Office reconsider its earlier ruling.
The Office said on Friday that scientists from Zurich's Federal Institute of Technology would be able to carry out their trials, but under certain conditions.
The GM wheat will have to be under permanent observation once it has been planted. The soil will be analysed to see if any of the modified genes have been transferred from the plants.
The researchers will also have to submit a report on the trial and its results, as well as carry out investigations on biological safety, including the effects of crosspollination and the toxicity of the GM wheat.
Difficult to assess
A series of physical safety measures will also have to be implemented. The plants have been modified to produce a protein that makes them resistant to a fungal disease.
When the previous decision was announced in November 2001, the Office had affirmed it was impossible to assess the risks involved in such a field trial.
"Man and the environment must not be exposed to an unknown product which on the basis of all the evidence we have is not necessary," said Philippe Roch, the Office's director, at the time.
The environment specialists had also voiced other concerns about the wheat crop, saying the DNA of the protein had not been fully described and that it was unclear what effect the modified genes might have on other plants.
But in September, after an appeal by the institute's researchers, Moritz Leuenberger told his colleagues to go back to the drawing board, saying the Office did have enough information available to make a proper risk assessment.
Leuenberger had judged that under Swiss law such outdoor tests could be carried out under strict conditions.
He had also noted that the Office had ignored recommendations by the Bio-Safety and Ethics Commissions, as well as from other federal offices, which favoured the research.
The Greenpeace environmental organisation had been outraged by Leuenberger's decision, accusing the minister of giving in to the GM lobby. Following the latest ruling, the NGO has reiterated its opposition to the field trial.
"The environment, people's health and biological agriculture must not be sacrificed for a useless and questionable experiment," wrote Greenpeace in a statement on Friday.
The commune of Lindau, in canton Zurich, said it was reassured by the safety measures that will be implemented. The council added that it was not against the trial, and was more preoccupied by aircraft noise bothering local citizens.
The tests will be the first carried out since the early 1990s, when modified potatoes were planted. Two other requests to grow GM crops outdoors were also turned down in 1999.
The Swiss have an uneasy relationship with GM technology.
While voters turned down a wide-ranging ban on genetically modified organisms in 1998, opinion polls have consistently shown that the public is widely opposed to GM crops.
This opposition has led Switzerland's two largest retailers, Migros and Coop, to refuse to stock any GM products.
swissinfo with agencies