DISGRACED car giant Volkswagen has admitted its own investigators have found "unexplained inconsistencies" in the carbon dioxide emissions from 800,000 vehicles.

The company already reeling from the revelation it fitted defeat devices to mask nitrogen oxide emissions in US emissions tests is expected to pay out another £1.4 billion bill to repair the new problem.

The firm refused to name the models affected, but said the flaw in no way compromised the safety of any cars.

Volkswagen said it will "endeavour to clarify the further course of action as quickly as possible and ensure the correct CO2 classification for the vehicles affected".

In yesterday's statement, the marque said it found data "inconsistencies" on carbon dioxide emissions for 800,000 more cars

The latest discovery in an internal inquiry mostly affects small diesel engines and one petrol mode.

It is unconnected to US regulators' allegations on Monday that larger diesel engines mostly used in Porsche and Audi SUVs were designed to cheat emissions tests.

The carmaker said it would immediately start talking to "responsible authorities" about what to do about the latest findings.

Volkswagen Chief Executive Matthias Mueller said: "From the very start I have pushed hard for the relentless and comprehensive clarification of events.

"We will stop at nothing and nobody. This is a painful process but it is our only alternative."

Europe's largest carmaker had previously admitted to installing cheat software on up to 11 million vehicles worldwide with two litre diesel engines.

A total of 1.2 million of the cars were expected to the UK market.

But the latest allegations from U.S. regulators and the automaker itself suggest that both larger and smaller motors and even non-diesel ones may have deceived regulators.

"VW is leaving us all speechless," said Arndt Ellinghorst of banking advisory firm Evercore ISI after the disclosure about the smaller engines. "It seems to us that this is another issue triggered by VW's internal investigation and potentially related to Europe."

VW has so far denied allegations regarding the larger 3.0 liter diesel engines made by the U.S. Environmental Protection Authority (EPA), saying no software had been installed to "alter emissions' characteristics in a forbidden manner" on the larger engines. It did not immediately respond to questions on Tuesday, saying it would only correspond in writing.

The biggest business crisis in VW's 78-year history has wiped as much as a third off its stock market value, forced out long-time CEO Martin Winterkorn and rocked the auto industry - a key employer and source of export income in Germany.

"Volkswagen has done a disservice to German industry," Ulrich Grillo, the head of the Federation of German industries, told a conference on Tuesday, adding the firm had an obligation to the whole industry to clear up the scandal quickly.

German Chancellor Angela Merkel and the European Commission, the European Union's executive body, called for clarity and transparency to clean up the scandal.

VW's supervisory board will hold a special meeting early next week to discuss the financial implications of the scandal, two sources with knowledge of the matter told Reuters.

The company took a 6.7 billion euro hit in third-quarter results to cover initial costs related to the scandal. Some analysts have said the final bill could reach as much as 35 billion euros in regulatory fines, lawsuits and vehicle refits.

The statement came after the Frankfurt Stock Exchange, where VW is listed, closed for the day. Earlier, the company's shares fell 1.5 percent to close at 111 euros.