Scottish Power has been doing more to tackle climate change than other large UK energy companies, a poll has found.
Scottish Power is praised for reducing carbon emissions
The environmental charity WWF ranked the six largest power companies on their performance on energy efficiency, CO2 emissions and renewable energy.
The charity said that while Scottish Power was reducing emissions, overall the power sector was doing little beyond trying to meet targets.
WWF Scotland called on the government to set more ambitious targets.
Dr Richard Dixon, the charity's director, said: "Scottish Power deserves praise for its reductions in CO2 emissions over the last year, but look at the bigger picture and there is still a long way to go."
The other companies ranked were E.ON UK, Scottish and Southern Energy, RWE/npower, Centrica and EDF Energy.
Scottish Power topped the green league for reducing its greenhouse gas emissions by more than 11% per KWh of energy generated in 2005.
It was also praised for a "strong commitment" to investing in renewable energy, with more than £1bn earmarked for renewable power generation up to 2010.
Scottish and Southern, which came third in the rankings, led the group on renewable energy.
Dr Dixon said: "It is no coincidence that the company most involved in nuclear power, EDF Energy, performs worst overall.
"The government needs to set much more ambitious targets to increase and diversify the use of renewable energy, cut energy waste and, in turn, reduce carbon emissions."
In Scotland, the energy sector was responsible for 37% of climate change emissions in 2003.
The report was released in the week that the government's energy review is expected to be published.