The German government's plans to alter rules on car tax from 2009 to take CO2 into account will likely be delayed further.

Reuters reported that the proposals were due to be signed off in cabinet next Tuesday but the finance, economy and environment ministries have been unable to reach final agreement and they are now due to be discussed in cabinet on June 18.

The measures, part of a climate protection package agreed last year, have stoked tensions within Germany's ruling conservative-Social Democrat coalition, Reuters noted.

Government sources said there was a risk the car tax changes will not now receive cabinet approval before the summer break.

Germany's previous government of Social Democrats and Greens, which ruled from 1998 until 2005, failed in its bid to change car tax rules to take account of exhaust emissions, mainly due to opposition from the states.

The climate package also contains new rules to promote environmentally friendly energy use in homes as well as plans to extend the reach and capacity of power supply cables, the report adds.