Speaking at the European unveiling of the new Toyota Prius, Thierry Dombreval, Toyota senior vice-president of sales and aftersales, called for more state support for hybrids and accused rivals of trying to water down future emissions regulations.
He said: 'At present 10 European countries have some form of encouragement for hybrids, with the UK being perhaps the most favourable with a Government-funded grant of about £1,000, but in many cases the support is not even national.
'We have a big task to convince governments of a need for support, and to ensure they understand the technology.
'We are competing against some big European players who are trying to reduce the gap between Euro IV and Euro V emissions limits.
'Although we don't yet know exactly what Euro V will require, our D-CAT diesel engines will be able to achieve Euro V compliance.
'European manufacturers want Euro V diesel rules to consist of Euro IV plus a particulate trap on vehicles, which is a cheap substitute. This holds back technology which is already available, and from an environmental standpoint is also unacceptable.'
Dombreval pointed out that the new Toyota Prius would produce one tonne less carbon dioxide in a year compared to the best performing upper-medium diesels.
He added: 'Diesel is heavily encouraged in Europe through lower taxation than petrol. If hybrids such as the Prius were to be treated as favourably it would give them the recognition and legitimacy they deserve.
But our European competitors are lobbying against reductions in CO2 emissions and oppose encouraging hybrids. This is not a friendly game, it's a war.'