Dealers handing over Volkswagen, Audi, Skoda and Seat new cars to fleet customers are being required to point out that the CO2 emissions quoted are only provisional.
Customers taking delivery are being asked to sign a letter confirming they understand that the CO2 figures and fuel economy figures may change from those currently stated.
And Volkswagen, Skoda, Audi, and Seat have all updated their website footers with the line "Our CO2 and consumption values are provisional and are currently under review. Revised values will be published if necessary."
AM’s sister title Fleet News has seen emails from the Volkswagen Group brands brands’ fleet directors to customers with lists of vehicles for which emissions and consumptions may be subject to change - mostly vehicles from 2015 or 16 model years.
Writing to Volkswagen customers, head of fleet Michael O'Shea said: "We want to make it clear to you that it may be necessary to publish revised, and potentially increased, values in the near future."
However, the Volkswagen Group has said that if additional tax is incurred, the company intends to cover the cost to fleets and company car drivers, adding: "We want to make clear to you that the Volkswagen Group has informed relevant government authorities of this issue and intends to settle those potential additional taxes."
Vehicles that may be affected are predominantly diesel, with 1.4, 1.6 and 2.0-litre TDI units included on the list, as well as the 1.4 TSI petrol engine.
This follows last week's announcement that some 800,000 vehicles globally may have higher CO2 emissions than stated.