A government energy review, to be published in July, is expected to recommend constructing new nuclear plants to replace Britain's ageing stations, most of which are due to expire by 2020.
But the Sustainable Development Commission warned that nuclear power alone could not plug the energy shortfall or tackle climate change.
The Sustainable Development Commission said the nuclear option "won't get us anywhere near tackling the U.K.'s energy and climate change crisis".
Chairman Jonathan Porritt called for an increased focus on energy efficiency, saying: "Even if nuclear gets the 'green light', it won't get us anywhere near tackling the U.K.'s energy and climate change crises, hence the crucial importance of getting it right on efficiency, renewables, heat and microgeneration."
"The government has been so busy trying to make the case for nuclear power it risks overlooking the much bigger challenges facing the U.K. today," he said.
"Even if the U.K.'s nuclear capacity is doubled, that would still leave 84 percent of total energy consumption unaccounted for."
The commission called for the country's "wasteful electricity network" to be upgraded to reduce energy loss, and "smart energy meters" and "sensible billing" to encourage consumers to use electricity more economically.
It also recommended increasing annual road tax to penalize drivers of the most environmentally-damaging vehicles, and "radical" building standards so that new houses would no longer need heating by 2010.
In April, the parliamentary Environmental Audit Committee said Britain needed gas-fired power stations as a new generation of nuclear plants would not be ready soon enough.