Speaking at a conference at the International Green Week in Berlin, the environmental pressure group said it had "collected enough data from around the world to be able to say that this product should have never been approved in the first place".
A new Greenpeace report claims that the GM soy in Romania covers more hectares than are officially registered. It says that conventional and organic farming is now impossible in many regions.
"Recent Greenpeace research in Romania has exposed the fact that since the company has introduced GM soy, things have gone totally out of control," said Susanne Fromwald from Greenpeace Central and Eastern Europe.
Dragos Dima, who left Monsanto in 1999 when GM soybeans were first introduced in Romania, said that the acreage of the herbicide resistant soybeans increased uncontrollably year after year.
"European member states should avoid Romania's example, protect European agriculture and oppose Monsanto's application," added Fromwald.
US giant Monsanto however believes that the tide of opinion is turning. The EU ordered Greece to lift its ban on Monsanto's GM maize MON 810 this week, saying that Greece does not have sufficient reasons to ban the Monsanto seeds, especially as EU scientists had already assessed MON 810 as safe for human health.
The firm also recently reported strong first quarter sales, largely on the back of a good performance from its seeds and genomics segment. According to the company, a key driver for the quarter was stronger-than-expected purchases of Roundup herbicides in the United States, Europe and Argentina.
Indeed global biotech crop acreage continues to increase, according to a study from the International Service for the Acquisition of Agri-biotech Applications (ISAAA). Last year, eight and a half million farmers in 21 countries planted biotech crops - an 11 per cent increase from the previous year.
The US biotech giant is now seeking to expand its involvement in Europe. In December 2005 an application was lodged with the EU asking to grow its GM Roundup Ready soybeans across the whole of Europe once its current licence - permitting the beans' import but not cultivation - expires in 2006.
But Greenpeace continues to oppose the proliferation of GM soy and is asking the European member states to reject Monsanto's application. Greece, along with a number of other Member States, has also consistently voted against any new GMO authorisations.