Members of the European Parliament have written to Commission President-elect Jean-Claude Juncker voicing their opposition to the potential merging of the energy and climate change portfolios.

The energy and climate portfolios would come under one commissioner and is most likely going to UK’s Jonathan Hill, according to a draft document obtained by EurActiv.

The two separate portfolios were previously the responsibility of Connie Hedegaard as climate action commissioner, and Günther Oettinger, in charge of energy in the outgoing Commission team.

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A letter co-signed by around 25 Conservative, Socialists, Liberals, and Green MEPs from the environment and energy committees labels the decision to join the two policy areas a mistake and explains why they should be kept separately.

The MEPs believe a joint portfolio will only weaken the role of the EU in future climate and energy negotiations at the international level that will culminate at the December 2015 UN climate conference in Paris.

“A year before the conclusion of a new global climate agreement, this is not the right time to send the opposite signal by not appointing a dedicated climate action Commissioner,” the letter said.

Frédéric Thoma, energy policy adviser at Greenpeace EU, said it is important who gets the job.

"A capable and proactive commissioner could help steer the EU towards a clean and sustainable energy system, as much as the wrong person could roll back energy and climate policy at least ten years," he said.

The new commissioner’s agenda will include the creation of the much talked-about Energy Union, the reduction of Europe's energy consumption, and the diversification of its energy mix. He will also have to negotiate with Russia to ensure a continuous flow of gas from and to EU member countries and its neighbours.

The MEPs recognise “the links between the two portfolios are undeniable and continued close coordination between the two will be essential”

Potential conflicts of interest could arise when managing two different portfolios, like when drilling for oil lead to deforestation. In such cases, MEPs think it should be decided “between Commissioners, rather than arbitrated behind closed doors of a Commission Directorate-General”.

The Parliament’s reaction could put pressure on Juncker to change his mind to nominate one person for two important EU policies. The distribution of portfolios is still under discussion and a lot can change until the new college of commissioners takes office.