The Prime Minister has been accused of a “dereliction of duty” after revealing that climate change has been excluded from her top priorities at this weekend’s G20 summit.

Theresa May left it off her list of key objectives despite the issue likely becoming the central task of the meeting of world leaders, following Donald Trump’s decision to quit the Paris Agreement on climate change.

The summit in Hamburg will see the Prime Minister meet Mr Trump one-on-one for the first time since he caused outrage by announcing the US would not implement the agreement as it stands.

Green campaigners reacted angrily to the Government’s exclusion environmental issues from its key priorities, demanding richer G20 nations follow the example of less developed countries committing to clean energy by 2050.

It comes after the Government was repeatedly taken to court over its air quality plan and amid concern that a long-awaited 25-year environment plan has been shelved by Ms May.

German Chancellor Angela Merkel has said tackling climate change is to be the key objective of the summit following the US’s withdrawal from the Paris climate pact.

In chairing the summit, Ms Merkel has said she will aim to guide discussions so that they furthered the goals of the agreement, which aims to limit global warming to well below 2C.

But a senior UK Government official revealed the British G20 delegation’s four objectives would not include the issue.

Instead, Ms May will focus on cutting off terrorist financing, global migration, modern slavery and “making the global economy work for everyone”.

Green party co-leader Caroline Lucas MP told The Independent: “It's extremely disappointing that the Government isn't priorisitising climate change at this summit.

“With Theresa May set for a bilateral with Donald Trump she should be putting action on climate change at the top of the agenda – and pressing the US President to reverse his disastrous decision to pull out of the Paris Agreement.

“Of course no one would argue that climate change should be the only topic at the G20 – and the Government's other priorities are clearly extremely important. But for the greatest threat we face to be relegated from the top four priorities is a dereliction of duty from this Government.”

Labour leader Jeremy Corbyn told The Independent: "Climate change can only be effectively tackled with international cooperation. The Government should be pushing hard for greater action and coordination at the global level at the G20 but have failed to mention climate change in their four objectives.

"Theresa May must stand up for people and the planet and be prepared to speak out to put pressure on Donald Trump to change course on his catastrophic decision to pull out of the Paris Climate Agreement."

NGOs also said climate change should be at the top of the agenda, warning that it was “real and it’s happening right now”.

Oxfam campaign director Steve Price-Thomas said: “In the aftermath of President Trump’s decision to quit the Paris Agreement, it’s up to the rest of the G20 countries to honour and implement the deal.

“Fossil fuels are not the future. While government subsidies for oil and coal only make the rich richer, the clean energy boom is creating opportunities for everyone. We’ve seen some of the poorest countries in the world commit to 100 per cent clean and renewable energy by 2050 – the G20 should follow their lead.”

On Wednesday a senior UK government official confirmed the PM would have a one on one meeting with Mr Trump and was “expected to raise climate change with the President”.

He said that the UK remains fully committed to the Paris Agreement and that the British Government “don't see any need for renegotiation”.

However, Downing Street has yet to specifically rule out a re-negotiation or supporting Mr Trump’s efforts to do so.

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At the start of June, the US President confirmed he would pull the US from the Paris Agreement.

Apparently misunderstanding the name of the treaty, he argued that he was “elected to represent the citizens of Pittsburgh, not Paris”.

“We are getting out, but we will start to negotiate, and we will see if we can make a deal that’s fair. And if we can, that’s great,” he said.

The leaders of France, Germany and Italy immediately issued a joint statement saying the Paris accord was “irreversible” and could not be renegotiated, but the UK has shied away from taking this explicit position.

Foreign Secretary Boris Johnson claimed on Thursday that the UK could act as a moderating force on the US President’s more extreme policies.

He said: “Our role, as the UK is to represent our own point of view, whether it is on Nato, the vital importance of Article 5 of Nato, whether it's on climate change, whether it's on the Iran nuclear accord - it's the UK that is actually helping, we think, to mitigate, to get some of those American attitudes and policies that are currently coming out of the White House into a better place.”

But the British Government’s own record on the environment is far from beyond question, especially given it is being taken to court for a third time over its latest attempt to produce an effective plan to reduce air pollution to within safe limits.

ClientEarth, a group of campaigning environmental lawyers, has twice successfully won court orders requiring Ministers to come up with a strategy that complies with European Union law.

A draft third attempt was published for public consultation shortly before the general election, but ClientEarth is due to argue that this latest version is still not good enough.

Green campaigners have also raised concerns that Michael Gove’s return to the cabinet, precipitated by Ms May’s need for political support in the wake of the election, has led to a key environmental plan being shelved.

The 25-year Government plan for the environment was first promised two years ago and had finally been expected in 2017, but The Independent revealed how officials now are not guaranteeing it coming this year.