"We are facing a climate cataclysm." Not the words of Extinction Rebellion or the head of Greenpeace, but the line today from newly appointed International Development Secretary Rory Stewart in response to calls from a committee of MPs for the UK to overhaul its aid spending strategy to prioritise climate action.

The International Development Committee (IDC) of MPs today published a damning report on the government's "incoherent" strategy, highlighting how between 2010 and 2016 the UK provided £4.8bn of development funding to fossil fuel projects, almost matching the £4.9bn provided for the International Climate Fund between 2011-17.

The Committee argued climate change is not just one of a number of issues the UK should address through aid spending, but "the single biggest threat to stability and wellbeing in some of the world's most vulnerable nations".

It added that spending on fossil fuel projects should only proceed in exceptional circumstances where projects can be shown to fit into a net zero emission economy in 2050, warning that the current approach would "nullify the effectiveness of wider aid spending".

In a surprisingly strongly worded intervention, Stewart signalled he broadly accepted the Committee's assessment, offering his own tacit criticism of his predecessor's record.

"We are facing a climate cataclysm," he said. "One million animal and plant species are threatened with extinction. We need to take radical steps or we - and our planet - will face an irreversible catastrophe. The ice shelf is shrinking, oceans are rising and global carbon emissions are increasing. This is before we even count the cost on humans."

The report came just a day after a major new UN study warned the world was facing an unprecedented pace of biodiversity loss with one million out of eight million known species now threatened with extinction. It also comes just a week after the House of Commons passed a motion declaring a climate emergency and the UK's Committee on Climate Change recommended the government adopt a new target to ensure net zero emissions from the economy by 2050.

Stewart said the report from the International Development Committee "makes for sobering reading".

"We need new ways of working and a new direction," he said. "We need wholesale change. I take this report very seriously. Although we have done much already to tackle climate change, I feel strongly we can do more. I am going to make tackling climate change increasingly central to DFID's work."

A spokesperson for DFiD stressed that tackling climate change was a priority for the government and highlighted how "the UK has supported 47 million people to cope with the effects of climate change, and helped people and businesses around the world avoid 10.4 million of tonnes of emissions - equivalent to taking over two million cars off the road".

However, Stewart said that as International Development Secretary he was committed to putting "climate and the environment at the heart of what this government does to protect our planet for future generations".

He also defended the government's target of spending 0.7 per cent of gross national income on aid, which has faced fierce criticism from some of his Conservative colleagues.

He said the target "makes a difference, not just to the developing world, but to the UK as well".

"I want to see more of the UK aid budget spent on climate and the environment, particularly on research and development," he added. "As climate extremes worsen, it is the world's poorest countries and communities which will be most affected, but this is a global issue. Tackling climate change is not only the right thing to do. It is a very smart thing to do. We all breathe the same air as people in China and India and tackling issues like climate change matters to us all. The UK cannot solve such problems alone."

The comments will further bolster Stewart's green credentials as he takes his place at the Cabinet table for the first time.

He has emerged as a May loyalist during the recent months of leadership speculation, making frequent media appearances to make the case for the government's Brexit deal. But he has also fuelled speculation that he could one day emerge as a leadership contender himself, and has made a number of forceful interventions in recent weeks in support of bolder action on climate change.

In his first major interview following his promotion over the weekend he told the Sunday Times that using aid spending to battle climate change was the "politically smart" approach to take given concern over the issue among younger voters.

While still in his previous role as Prison's Minister he also published an article on the influential ConservativeHome website declaring that "of course there is… a climate emergency" and making the case for using centre right policies to drive climate action and clean tech innovation.

Stewart's promotion will strengthen the Cabinet's green wing as a series of crucial environmental policy decisions loom.

The government is widely tipped to accept the recommendations of the CCC and adopt a new net zero emission target, but a host of more specific policy decisions are likely to spark political rows as Ministers face growing pressure to strengthen their Green Brexit plans and deliver an autumn Spending Review that prioritises climate action and ensures medium term carbon targets are met.