By Mark Kinver
Science and environment reporter, BBC News
Progress on cutting CO2 emissions is too slow, the commission warns
UK government departments are not on course to meet their own targets for reducing carbon emissions, according to the Sustainable Development Commission.
The government's environmental watchdog warned that more needed to be done if emissions were to be cut by 12.5% from 1999-2000 levels by 2011-12.
In an assessment, it called on the government estate to "lead by example".
But the commission said departments had made good progress in some areas, particularly waste reduction.
"The government has taken some really significant steps in making its own operations more sustainable," said Rebecca Willis, the commission's vice-chairwoman.
"But it is still not on track to meet crucial targets, including reducing carbon emissions from offices," she added.
"Worryingly, the current targets themselves do not match the scale of the challenge we face, particularly on climate change."
In its Sustainable Development in Government 2008 report, the commission said that the government reported a 6.8% reduction in carbon emissions from offices.
But it concluded: "This is not sufficient to be on track to meet the target of reducing emissions by 12.5% by 2011-12, and far from enough to contribute to the national target of an 80% reduction by 2050."
It added that a £4bn investment in wind and solar energy generation on the government estate would "immediately cut emissions from offices by 68%".
The report also showed that government departments and agencies had been able to reduce waste beyond the set targets.
The goal was for departments to reduce their waste by 5% from 2004-05 levels by 2010, and by 25% by 2020. However, the data showed that, across government, waste had been cut by 28.8%.
"Significant progress has been made by the government in delivering on its commitment to deliver sustainable operations," said William Jordan, central government's chief sustainability officer.
"The government will be this year revising its targets and commitments to ensure that these reflect leading practice on sustainability."