David v Ed – which Miliband will be best for green business?

In his latest (I'd like to say final, but we all know that won't be the case) attempt to clip the wings of the party he purported to lead, Tony Blair chose the same day as the start of the Labour leadership ballot to release his 718-page, score-settling confessional, A Journey.

In one fell swoop Blair's ego-smear has overshadowed and, through his tacit and unwanted endorsement of David Miliband, influenced a Labour leadership election that could prove to be the most important political contest of the next four and a half years.

But leaving the fallout from Blair's virtual admission that he always was a Conservative fifth columnist to those better qualified to comment, it is worth looking forward rather than back and asking how the Labour leadership election could affect the UK's climate change policy.

With the contest boiling down to a straight run-off between the brothers Miliband, it seems certain the next Labour leader will have a strong affinity for environmental issues and an excellent understanding of climate change policy – a fact that will inevitably shape the coalition's actions, regardless of whether or not a Miliband becomes the next resident of 10 Downing Street.

The emergence of the Milibands as the two leading candidates for the Labour leadership will come as a relief to green business leaders across the UK.

Ed Balls, like his mentor Gordon Brown, has always appeared as being a man who would happily concrete over the Cotswolds if it would win him a one-point lead over the Tories, while Andy Burnham's and Diane Abbott's combined pronouncements on climate change would fail to cover the back of a postage stamp.

In contrast, both David and Ed Miliband made their names through environmentally focused ministerial positions, David as secretary of state at Defra between May 2006 and June 2007, and Ed at the newly created Department of Energy and Climate Change from June 2007 until the election in May.

As such, both Milibands have played a key role in the under-reported transformation of the UK's low-carbon policy over the past four years. David laid the foundations by forcing climate change up the political agenda, establishing the UK as one of the leading advocates of low-carbon action in the EU, and shaping the country's flagship climate change bill. His brother then built on that work by delivering a series of new policies, such as the feed-in tariff and interventionist funding for low-carbon businesses, while also securing a starring role at the ill-fated Copenhagen summit.

As with so many other aspects of the race, the question of who would make the most effective Labour Party leader and prospective prime minister is difficult to resolve.

Ed Miliband has the reputation of being the more radical politician and has been (largely unfairly) positioned as the candidate of the old Labour left. But it is worth noting that it was David Miliband who first floated the idea of personal carbon credit cards, a highly radical and redistributive proposal that would effectively introduce a cap-and-trade scheme for individuals. It is also worth noting there are whispers suggesting Miliband senior has not completely abandoned the idea and would happily revive plans to pilot the inevitably controversial project.

In addition, David has publicly committed to raising taxes in the financial sector to pay for low-carbon investments, stating on his campaign web site that his leadership would "promote manufacturing through a new industrial revolution – starting by doubling the levy on banks and investing in green jobs". He is also the more experienced politician and a solid media performer, even if the perception of him as a policy geek refuses to die away.

Ed Miliband is similarly committed to the interventionist low-carbon industrial policy that the Labour government was beginning to flesh out before it was interrupted by the electorate. Despite being in the throes of a leadership contest, Miliband has emerged as one of the most vocal and effective shadow ministers in the opposition, slamming the coalition for withdrawing support for nuclear components manufacturer Sheffield Forgemasters and pillorying claims that the current government will be the greenest ever.

He also has the people and presentational skills that his brother arguably lacks. Having seen him speak at numerous meetings and conferences during his time as climate change secretary, I can attest that the younger Miliband has the priceless political ability to charm a room – once even prompting a PR in the press room at one conference to describe the minister as her "unexpected crush of the day". It is hard to imagine him developing the authority required to land blows on David Cameron during Prime Minister's Questions in the Commons and judging by the pre-election hustings he occasionally struggles to hide his frustrations with rivals. But it is easy to see why, when face to face with the electorate, he has proven such an energetic and effective campaigner.