Of 1,834 individual diesel models currently on sale in the UK, fewer than 200 achieve the tough emissions standard due to come into force in 2005.
Company car drivers in diesels can benefit from those that comply with Euro IV because they are not subject to the 3% diesel supplement.
But although manufacturers are claiming to be on course to meet the new standards, slow progress reflects uncertainty in the market on the best way to achieve compliance.
Some of the technical solutions available to reduce nitrous oxide and particle emissions so Euro IV can be achieved can increase carbon dioxide emissions, offsetting any advantage for the company car driver.
CAP is urging manufacturers to prioritise the issue as the majority of new diesel buyers are leasing companies and large fleets.
New Vehicle Database manager Helen Butterworth, said: 'With only about 10% of diesels currently Euro IV compliant, this is an urgent issue for manufacturers and fleets.
'Drivers choosing cars now, which will remain tax efficient during their whole term, are faced with little choice at the moment and this means potential opportunities for corporate sales are being missed.
'Among the difficulties faced by the manufacturers is that some of the equipment needed to adjust the emissions can add in the region of £500 to the cost of the car. If this is passed through to the end user then the tax advantages of compliance are potentially wiped out.
'Unfortunately there is no simple solution as long as we have a UK policy based on CO2 emissions and a European-driven policy on reducing other types of emissions.'