By Mark Kinver
Science and environment reporter, BBC News
Ed Miliband is viewed as a rising star of the Labour Party
Green groups have welcomed the creation of a new energy and climate department in Gordon Brown's government reshuffle.
Ed Miliband will head the new department, and will join his elder brother David around the Cabinet table.
Previously, the UK's energy policy and climate strategy has been divided between two separate government teams.
Think-tank Green Alliance said it hoped the move would result in a more joined-up approach to cutting emissions.
"Hallelujah. A department of energy and climate change, and not before time," responded the alliance's director, Stephen Hale.
"Ed Miliband's in-tray is piled high with issues that the old structure did not resolve. The new department puts climate change where it belongs, with its own seat at the cabinet table."
The CBI described climate change and energy security as "vital national interests", adding that both required urgent action.
"Combining them may help identify both synergies and trade-offs, but we must avoid either one becoming subordinate to the other," said Dr Neil Bentley, the CBI director of business environment.
"Ultimately, it is sound, timely policy decisions that matter most, not departmental names or structures."
Bridging the divide
Commentators say Mr Miliband's appointment offers an indication of how important the prime minister views the issues of energy security and climate change.
The former Cabinet Office minister had been trusted with the task of co-ordinating the Labour Party's election manifesto before being moved into this new ministerial post.
It has been a longstanding criticism from environmentalists that the UK's energy policy and climate change brief had been divided between different departments.
The Sustainable Development Commission (SDC), set up by Tony Blair to act as the prime ministerial environmental advisory body, saw the formation of the new department as a step in the right direction.
The commission's vice chairwoman, Rebecca Willis, said it was something that the SDC had been wanting to see happen for a number of years.
"This change will make it far easier to make joined-up decisions in an area which is crucial for the UK and the world," she told BBC News.
"By making the right sustainable energy choices, we can tackle energy security and climate change together, and we look forward to working with Ed Miliband to this make this happen."
The news was given a more cautious welcome by the Policy Exchange, a free market think-tank.
"Whether a new energy and climate change department under Ed Miliband's leadership can sort out the current UK energy policy mess is far from certain," observed the group's head of environment, Ben Caldecott.
He told BBC News that important questions still needed to be answered: "For example, will this new department now take over international climate change negotiations from Defra?
"Is it going to suffer from the same problems that made energy policy making in Berr so difficult and biased towards nuclear and wind?
"Given this government's track record on energy policy - we're in the third energy consultation in 11 years - I doubt shifting civil servants around Whitehall is going to make very much difference before a general election."
Until now, the Department for Business, Enterprise and Regulatory Reform (Berr) had responsibility for the nation's energy strategy and ensuring the lights did not go out, while the Department for Environment, Food and Rural Affairs (Defra) had the task of trying to curb the rise of greenhouse gases and ensuring energy was used more efficiently.
It was believed that Defra was the weaker sibling and often lost internal struggles to the more powerful Berr in the clumsy policy partnership, which green groups described as a perfect example of an antonym of joined-up thinking.
Downing Street has yet to announce the make-up of Mr Miliband's ministerial team.