* EU proposal seeks to prevent repeat of VW scandal
* Germany opposing key parts of the reforms - document (Adds further detail from document, background)
FRANKFURT/BRUSSELS, April 25 (Reuters) - Germany is opposing key elements of a European Union proposal to overhaul how car engine emissions are tested for pollution, a document seen by Reuters showed, as Brussels attempts to prevent a repeat of the Volkswagen emissions scandal.
The German carmaker's admission in September 2015 that it used software to cheat U.S. diesel emission tests also highlighted the laxness of the EU's own tests, prompting the European Commission to seek broader supervisory powers, including the ability to impose fines on carmakers.
Vehicle emissions testing and supervision is currently organised on a national rather than a pan-European level.
A German position paper seen by Reuters shows that Berlin is against allowing Brussels to fine car makers up to 30,000 euros ($31,925) per vehicle
EU proposals also include making governments rather than car makers pay for emissions testing. Under the Commission's proposal, EU nations would have to fund car exhaust testing centres, although they can levy fees from car makers to do so.
Germany is in favour of keeping vehicle testing and vehicle licensing a national affair, the German position paper showed. How tests are funded should also remain a matter for national authorities, the German paper showed.
Germany instead proposes that the independence and supervisory powers of national authorities be strengthened to improve the effectiveness of spot checks on polluting cars, regardless of how these tests are financed.
It also suggests that carmakers test cars on certified test benches operated solely by vehicle approval authorities, rather than at testing facilities owned by the carmakers.
Cheating emissions tests has become harder since European regulators introduced a more stringent testing regime, known as RDE, designed to reflect everyday driving conditions and to narrow the disparity between road and laboratory test results.
Germany is not alone in stalling. An inquiry by the European Parliament has accused EU member governments including Italy, France and Spain of repeatedly delaying the adoption of stricter car emissions tests, despite evidence that this has allowed pollution to go above legal limits.
No manufacturer other than VW has been found to have installed software designed solely for the purpose of circumventing emissions tests, but regulators in Britain and Germany say that carmakers have made extensive use of a "thermal window" which allows manufacturers to turn down pollution-control systems for the sake of protecting an engine.
Brussels is becoming increasingly frustrated by what it sees as governments colluding with car makers. It launched legal cases against Germany, Britain and five other EU members in December and has promised more cases to come.
Since the VW scandal broke other European carmakers including Renault, PSA Group, Fiat Chrysler and Daimler have been drawn into investigations concerning diesel emissions.
While EU member states are still debating the EU's proposal, expecting to hammer out a final position by the end of May, the European Parliament has endorsed the Commission's bill.
The legislation will then be finalised in negotiations between the EU's three law-making bodies.
"We invite the co-legislators to uphold our level of ambition so that we introduce greater quality and independence in vehicle testing, more surveillance of cars already in circulation, and greater European oversight," a spokeswoman for the European Commission said. (Reporting by Alissa de Carbonnel in Brussels and Edward Taylor in Frankfurt; editing by David Clarke, Greg Mahlich)