The European Parliament on Thursday demanded "immediate clarification" from Washington on claims of U.S. spying on EU offices and warned the espionage scandal could damage diplomatic ties.

In a resolution overwhelmingly adopted in the Strasbourg-based legislature, MEPs said the parliament "strongly condemns the spying on EU representations" and warned of its "potential impact on trans-Atlantic relations".

It called for "immediate clarification from the U.S. authorities on the matter".

Lawmakers however rejected an amendment by left and far-left parliamentarians to call for the postponement of talks on a vast EU-U.S. trade deal, which are due to start on Monday.

Another amendment was rejected calling for EU states to grant asylum to fugitive intelligence leaker Edward Snowden, a former contractor with the National Security Agency (NSA) who revealed the widespread bugging of EU diplomatic missions and offices.

Despite initial calls from France for a delay in the trade talks, the EU said Wednesday they would go ahead as planned but run in tandem with working groups tasked with probing the extent of U.S. spying. (AFP)