In the original farm-scale evaluations, scientists studied the effects on biodiversity of four GM species - spring oilseed rape, winter oilseed rape, sugar beet and maize.
They concluded that while GM spring rape and sugar beet are more harmful to the environment than their conventional equivalents, GM maize is actually better for biodiversity.
Tracking the quantity of weed seeds in the soil of these crops, the new study suggests that the original results observed for GM rape and maize continue to persist for up to two years.
Interestingly, writes CORDIS, in those areas sown with sugar beet that had seen a decline in the weed seedbank during the original study, the follow-up analysis suggests a partial recovery of the seedbank has taken place.
Les Firbank, the FSE project coordinator told the BBC News website he does not believe that the new results will affect any decisions on approving GM crops in the UK.
Following the initial FSE results, the government indicated that it would approve cultivation of the GM maize crop used in the study. But its manufacturer, Bayer, has not opted to go ahead with European clearance.