Image copyright Getty Images Image caption Ed Miliband urged the prime minister to ratify the Paris deal before he goes

Prime Minister David Cameron has been urged to ratify the Paris climate agreement before leaving office.

Labour’s former climate change secretary Ed Miliband said "climate sceptics" might try to derail the deal if they gained positions of power following the EU referendum.

Government sources told BBC News that the Brexit vote would not alter ministers' plans on the agreement.

But the sources did not offer any firm timetable for its ratification either.

A deal to attempt to limit the rise in global temperatures to less than 2C was agreed in Paris at the end of last year after two weeks of intense negotiations.

About 175 countries have signed up to the deal to cut carbon emissions. But each of those nations has to go a step further by formally "joining" or ratifying the deal in the form of a communication to the UN.

Paris climate deal: In summary

Already some analysts are warning that Brexit will spell the end of French government support for the Hinkley nuclear station.

But most of the key decisions affecting the UK will be taken by the next prime minister and the people chosen to run the Department of Energy and Climate Change (Decc) and the Department of the Environment, Food and Rural Affairs (Defra).

Of the front-runners for the Conservative leadership, Boris Johnson has given contradictory messages on climate change over the years. He promised to make London a low-carbon energy leader, but has also cast doubt on climate science.

Michael Gove previously spoke in favour of tackling climate change, but then tried to trim the school curriculum by dropping mandatory climate change lessons - a plan that was beaten down.

Theresa May doesn’t appear to have spoken publicly on the climate.

Among other possible leadership candidates, Energy Secretary Amber Rudd and Energy Minister Andrea Leadsom both supported increased ambition for the UK on climate change whilst imposing huge cuts on renewables subsidies.

Stephen Crabb has called climate change the greatest challenge of this and future generations.

Jeremy Hunt says Conservative promises on climate change are sincere, and has generally voted with the government on climate change.

'Massive' challenge

Mr Miliband told me: "I take David Cameron at his word that he cared about these issues - but we don’t know who’s going to succeed him.

“He should ratify the agreement before he leaves office because we don't want to end up with a climate change denier or sceptic as prime minister who tries to renegotiate the whole thing.

“It’s the biggest single issue facing our world; the biggest single issue facing my kids as to whether we step up on this. We have a massive, massive challenge and we’ve got to get on with it.

“The French have ratified [the Paris agreement] and as I understand it’s perfectly in our gift to get it done. There is a majority in the House of Commons for it – so we should get on and do it."

Only a handful of MPs voted against the Climate Change Act in 2008, and most Conservative MPs broadly support decarbonisation. But there are known ties between Euro-scepticism and climate scepticism.

Image copyright AFP Image caption Environmentalists say climate policy has already been undermined by cuts to renewables subsidies

Lord Lawson, who founded the climate sceptic pressure group Global Warming Policy Forum, was involved in the Leave campaign. Several Euro-sceptic and climate sceptic groups are housed in the same Westminster property, 55 Tufton Street.

And the overlapping groups say both climate change policies and the EU interfere with markets and restrict choice.

The Leave campaign complained that EU renewables targets have pushed up the cost of energy and warned that the UK’s energy security will be reduced if coal plants are shut.

They said that if the UK left the EU, domestic energy bills could be cut by removing VAT on home heating and lighting.

Mr Miliband said he would support action to scrap "regressive" VAT on bills, but he said a big campaign to insulate homes should be introduced too.

His fears over the impact of Brexit on climate policy have been widely voiced by environmentalists. Much of our energy and environmental policy is formed in Brussels - including rules on state aid for energy; targets for carbon reduction, energy efficiency and renewables; and new product standards.

Standards were a campaign target by Leave supporters who argued that the EU would deny people powerful vacuum cleaners. Experts said efficiency standards would reduce energy cost and emissions without compromising performance.

The EU has brought a huge improvement in UK environment policy on issues like waste, sewage, beaches, air pollution, environmental protection, marine conservation, and resource efficiency - albeit at a cost to taxpayers and bill-payers.

Some of these improvements - like water treatment - entail huge infrastructure investment that won't be undone. And there is no certainty that laws on environment and energy will be watered down in a new government.

In fact, some Leave campaigners argue that on issues like farm subsidies and fishing, the UK will protect the environment better than the EU.

But the Global Warming Policy Forum – influential amongst Conservative MPs – warned in its latest policy note: “Since the UK will need to sail fast and free post-Brexit, the economic engine must be fuelled as cheaply and efficiently as possible, a requirement that is incompatible with currently applicable EU (climate) regulation, and much of it will consequently have to be rejected.”

It pointed to 230 rules affecting energy supply and called for the speedy rejection of three major planks of EU climate policy: the emissions trading scheme, which increases the cost of pollution for big business; the Industrial Emissions Directive which cuts pollution from power plant; and the Renewables Directive, which requires the UK to obtain 15% of total energy from renewables by 2020.

Given that the UK played a major role in the Paris climate deal and has also urged the EU to increase ambition on climate change, it would represent a massive reversal to reject EU energy and climate policy at home.

But environmentalists complain that that policy has already been undermined by wholesale cuts to renewables subsidies imposed by George Osborne.

Mr Miliband was been accused by critics of inadvertently provoking the government’s subsidy cuts by promising during the last election campaign to freeze power bills. His critics say that forced Mr Osborne into a political corner where he was obliged to cut subsidies in order to trim bills.

Mr Miliband rejected that accusation.

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