Only a handful of GMO crops may be grown commercially on EU territory, mostly maize types. These crop approvals were issued in 1997 and 1998, before the bloc began a six-year moratorium on new GMO authorisations that ended in May 2004.

"This task should be prioritised to take account of the types of GM plants released within the Community at the present time and those predicted in the near future," the notice said.

Last week the Commission held its first debate on GMO policy in more than a year, vowing to press ahead with authorising more gene-altered crops and foods even if EU governments could not break years of deadlock over the issue.

While new approvals are trickling in, they have so far related to imported GMOs for use in food, animal feed and industrial processing. No GMO crop has been won EU approval for planting since 1998.

"This study is partly about finding out where the gaps are. There are still some things about GMOs that we don't know...but we know more about them now than we did at the time (in 1997 and 1998)," a Commission official told Reuters.

But green groups said the tender demonstrated how little EU research had been conducted on the long-term effects of GMOs on human and animal health, as well as on the environment.

"We've a huge debate (on GMOs) for eight years and in that time there have been no long-term studies," said Adrian Bebb, GMO campaigner at environment group Friends of the Earth.

"Consumers have been exposed to this, animals on farms have been exposed to eating huge amounts of GM feed with no long-term study," he said. "And they (Commission) are now admitting they haven't done the research because they're calling a tender."