Diplomats from Germany, home to disgraced auto giant Volkswagen, have lobbied behind the scenes to maintain European pollution tests that are widely considered ineffective, leaked documents seen by AFP showed on Thursday.

The German position papers, first reported by The Guardian newspaper, ask that EU regulators maintain crucial loopholes in updated car tests that would allow for greater carbon dioxide emissions than revealed in official results, activists said.

The Guardian reported the existence of similarly argued position papers by France and Britain.

The technical documents, dated from last May, relate to tests that measure carbon (or CO2) emissions and not the nitrogen oxide pollutants that have been the focus of the Volkswagen uproar.

The papers specifically argue for limits on how the old CO2 test system, known as the NEDC, should be changed to match the stringency of the new one (WLTP).

In the papers, Germany asks for the correlated test to take place with bigger exceptions than proposed so far by the EU, including the permission to hold the test on tracks that slope downhill.

Activists say this lobbying exposes the hypocrisy of major EU member states that have criticised Volkswagen for rigging pollution tests, while pushing in secret for weaker testing.

"It's sheer hypocrisy for the three biggest European countries to demand an EU investigation on VW's cheating and at the same time lobby to weaken the new test through the backdoor," said Greg Archer, clean vehicles manager of Transport & Environment campaign group.

The European Commission, which handles the standards of pollution testing in the 28-member EU, refused to comment directly on the reports of lobbying.

"We are counting on the support of member states to not only be very strict in complying with rules but also to improve our standards so that they are much more robust," EU commission spokeswoman Lucia Caudet said at a news briefing.