Volkswagen has contacted the Irish Government warning that extra tax payments may be due on cars affected by the company's emission test cheating scandal.

In a letter to Finance Minister, Michael Noonan, the company's chief executive, Matthias Müller revealed that the incorrect CO2 values registered by its vehicles in test conditions, "could affect taxes or other public charges already assessed or to be assessed."

He added that Volkswagen will meet the cost of any increase in the tax liability on these diesel vehicles.

The letter - which has been seen by The Irish Times - states that Mr Müller, "guarantees that potential additional taxes will be settled by Volkswagen Group," and that Volkswagen, Audi, Seat and Skoda models may be affected.

It continues to request that customers have no involvement in the levelling of retrospective charges, saying, "We would be grateful if also you would be willing to allow – if necessary through legal or administrative measures – that the competent tax authorities do not impose any potential additional public charges to our customers but rather to Volkswagen directly."

New directives have also been put in place in Irish car dealerships who sell models which may have been involved in fraudulent tests. They have been issued with forms for customers - confirming that they have been made aware that the emission readings attached to these vehicles "may be inaccurate."

The company's own investigation has concluded that the software which was used to cheat tests could have been installed in as many as 11 million vehicles.