GERMAN prosecutors have launched an investigation into fraud allegations against former Volkswagen boss Martin Winterkorn, as subsidiary brands Audi and Skoda confirmed they have a total of 3.3 million cars fitted with the emissions cheating software at the centre of the scandal.

The German prosecutor's office said it was investigating Mr Winterkorn over "allegations of fraud in the sale of cars with manipulated emissions data" based on charges filed by about 10 unidentified individuals.

Mr Winterkorn quit as chief executive of the Volkswagon Group on Friday, but stressed he was not aware of any wrongdoing on his part and wanted to give the company a new start.

The Volkswagon Group is also understood to have suspended three top engineers as it tries to get to grips with a crisis that has knocked more than a third off its market value and could harm Germany's economy.

According to reports on Monday, Heinz-Jakob Neusser, head of brand development at VW has been suspended along with Ulrich Hackenberg, the head of research and development at premium brand Audi who oversees technical development across the group, and Wolfgang Hatz, research and development chief at sports-car subsidiary Porsche, who heads group engine and transmissions development.

Volkswagen has admitted cheating diesel emissions tests in the United States but Germany's transport minister says it also manipulated tests in Europe, where it has much bigger sales, and it faces the worst business crisis in its 78-year history.

The crisis is an embarrassment for Germany, which has for years held up Volkswagen as a model of its engineering prowess and has lobbied against some tighter regulations on car manufacturers. The German car industry employs more than 750,000 people and is a major source of export income.

On Monday, Audi and Skoda confirmed that they have a total of 3.3 million cars fitted with the software that allowed parent company Volkswagen to cheat US emissions tests.

Some 2.1 million Audis affected worldwide include 1.42 million in western Europe, with 577,000 in Germany, and almost 13,000 in the United States.

The Audi models affected include the A1, A3, A4, A5, A6, TT, Q3 and Q5 models.

Czech-based Skoda said 1.2 million of its cars were involved, but has yet to give a country or model breakdown.