Multiple reports claim the measure will be revealed by business secretary Lord Mandelson this afternoon in his speech to the Labour Party conference.
As it currently stands the scheme will end either in February or when the £300m the Government has put into the scheme runs out.
This was expected to be next month, but according to The Guardian, Mandelson will announce that the Government will put in enough new money to cover 100,000 more vehicles and the scheme will also be expanded to cover vans purchased before September 2002.
The scheme is estimated to have enabled the replacement of around 200,000 vehicles so far.