The scrappage scheme is set to end in chaos as some car manufacturers are unable to tell potential customers whether they are allowed to accept deals.
Limited funds remain for the scheme, which is due to finish at the end of this month, and as a result quotas are being allocated to manufacturers according to how popular their cars have been during the incentive.
However, the Department for Business Innovation and Skills (BIS), which administers the scheme, is struggling to release each manufacturer's quotas because the figure is continually changing.
This has bene complicated as some manufacturers have not reported scrappage sales fortnightly as required, and several have cancelled scrappage orders - reports suggest one manufacturer cancelled 3000 scrappage orders in one go recently.
BIS has declined to name the car makers that haven't complied with the rules.
It is possible for BIS to withhold the government's £1000 portion of the incentive as punishment for manufacturers that have not met the rules, but this is thought to be unlikely to happen.