According to new figures from Swedish car industry organization Bil Sweden, 36,611 greener cars were registered in 2006, accounting for 13.5 percent of all private cars registered.
A total of 282,632 new cars were registered in Sweden in 2006 - three percent more than in 2005.
The rise in the number of new green cars could have been greater if the government had put into practice its election promise of a 10,000 kronor 'green bonus' tax break on the vehicles, Bil Sweden's Bertil Moldén said.
"My impression is that many people are waiting to see what happens with that," Moldén told news agency TT.
The Swedish Association of Green Motorists' spokesman Mattias Goldmann said that there were a number of question marks over the future of alternative-fuel cars in Sweden:
"Will there be a green bonus? Will there be measures to increase ethanol sales? Will congestion charging come back and will green cars be exempted," he asked.
Environment minister Andreas Carlgren's spokesman Tomas Uddin said that the government was working on the question.
"We will introduce the green bonus and we expect a decision during the spring," he said.
Bil Sweden is demanding that the government give alternative fuels the support they need.
"Price differences must increase. It is currently cheaper to fill up with petrol than to use the alternative fuels such as ethanol. VAT on ethanol should therefore be reduced to six percent," Bertil Moldén argues.
Tomas Uddin counters that EU rules make it "hard to favour one form of energy in that way," but said that the government announced before Christmas that it would spend 150 billion kronor to encourage the building of new biogas pumps.