BRUSSELS (Reuters) - European Union regulators launched legal action against Poland at Europe's highest court on Thursday for the country's move to ban the trade in and planting of genetically modified seeds, the EU executive said.

Poland's plans for what amounts to a national GMO ban, announced last year, quickly drew criticism from European Commission lawyers who routinely scrutinise any such proposals.

Earlier this month, they said it had no scientific justification. But Poland's insistence in proceeding with the ban, despite several warning letters sent from Brussels, meant the Commission now had to resort to legal action, it said.

'On the basis of the information provided by the Polish authorities in their replies to these letters, the Commission has no alternative but to refer Poland to the ECJ,' it said, referring to the Luxembourg-based European Court of Justice.

'In their reply, the Polish authorities confirm their intention to maintain the ban Polish authorities believe that the use of GM seeds encroaches on the sphere of public morality, an encroachment that would justify a total ban on GM seeds.'

As tested on several previous occasions, the Commission takes the view that if a region wants to ban GMO crops or products, such restrictions must be scientifically justified and crop-specific to comply with EU law.

It also believes that a proposed ban must not be politically motivated, or a blanket GMO restriction that might distort the EU's single trading market.

Poland's law on seeds and plant protection, adopted in April 2006, introduced a total ban of trade in GMO seeds varieties on Polish territory.

Since the use and trade of GMO seeds was harmonized across EU member countries, the Commission had told Poland -- in a first letter sent in October 2006 and then in another sent in June 2007 -- that its GMO ban broke EU law, the statement said.

(Reporting by Jeremy Smith; editing by Chris Johnson)