BRUSSELS (Reuters) - Volkswagen's (VW) <VOWG_p.DE> technical fix for one of the vehicles involved in its "Dieselgate" scandal did not reduce emissions in a test, a European consumer group said on Thursday.

VW has argued the fix for vehicles affected by its emissions test cheating scandal would make them compliant with EU regulations, avoiding the need to compensate owners.

Pressure has built on VW to offer financial compensation to customers in Europe after the carmaker agreed to pay out up to $15.3 billion in the United States to settle claims.

The test of the Audi Q5 by the Italian consumer group Altroconsumo showed harmful nitrogen oxide (NOx) emissions 25 percent higher after the removal of illegal defeat device software than before the technical fix, the European Consumer Organisation (BEUC) said.

VW was not immediately available to comment.

"VW's solution to deactivate the defeat device is not reliable," BEUC's head Monique Goyens said in a statement.

"VW must compensate European consumers," she added. "National public authorities must finally take action and put pressure on VW to correct their misbehavior."

While the EU's industry commissioner has urged VW not to treat U.S. and European customers differently, despite differing legal systems, responsibility for policing, penalties and enforcement in the EU lies mainly with national authorities.

Legal wiggle room over whether software used to switch off emissions controls contravene EU law has muddied the waters, with automakers saying they are allowed to protect engines against potential damage.

A spokeswoman for the EU executive said it had asked for additional information on why reports by German and British regulators in April found evidence of so-called defeat devices but deemed them legal.

Last week, EU Industry Commissioner Elzbieta Bienkowska took carmakers to task, saying they stretched the legal bounds, for instance with emissions control systems that switch off at below 17 degrees Celsius.

"That means in Northern Finland you drive without emission control almost all year-long," she said at an industry gathering. "What you do is you make the exception the general rule."

(Reporting by Alissa de Carbonnel; Editing by Mark Potter)