Germany's transport ministry has denied that it had known about the technology Volkswagen used to cheat emissions tests despite acknowledging only months ago that it knew of a general gap between 'test' and on-road emissions.

Volkswagen has admitted used software to recognise when a car was being checked in a test centre, switching the engine to economy mode and injecting chemicals to cut emissions in order to record 'test' results below those seen in normal driving conditions.

Earlier this year, members of the Green party challenged the government on the discrepancy between emissions in the test environment and during normal driving.

The transport ministry, responding for the government, acknowledged in a July 28 statement that it was aware of the issue and that it was seeking tighter rules. The answer did not, however, recognise any deliberate rigging.

"Through the improvement and reconfiguration of the measurement process, through the fixing of far lower tolerance levels as well as using conditions that are closer to reality, the aim is to get a more representative results," the government said in its answer.

It acknowledged that not enough had been done to address emissions control devices and said it was working on new 'technical rules'. The introduction of those rules, it added, was being negotiated with the European Union's executive, the European Commission.

A German newspaper, die Welt, said the answer was tantamount to admitting that it knew of the car emissions "tricks" but a spokesman denied this.

"There was no knowledge at the Transport Ministry about the use of emissions control technology," he said.  - Reuters