Lord Cameron, speaking on a visit to Ukraine, also underlined the importance of supporting the Ukrainian war effort against Russia, warning that the world was at an "absolutely critical tipping point" and Kyiv must prevail or else Europe faced a "very dangerous future".

However, he cautioned against an idea from French President Emmanuel Macron to consider sending NATO troops to Ukraine to join the fight if Russia's Vladimir Putin achieves a breakthrough, saying that such a move would be a "dangerous escalation".

"I don't think it is right to have NATO soldiers killing Russian soldiers," the foreign secretary said in an interview in the western city of Lviv on Friday, having met President Volodymyr Zelenskyy and other top ministers in Kyiv on Thursday.

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Lord Cameron made the two-day trip to reaffirm the UK's commitment to Ukraine, which most recently includes a promise to transfer more of the British military's own stockpiles of weapons, including precision-guided bombs and air defence missiles.

The UK has also promised at least £3bn worth of military assistance annually.

But Western nations are failing to deliver munitions to Ukraine's frontline as quickly as Russia is rearming its military, with Russian troops gaining ground in the east in recent months.

President Putin put his economy on a war footing when he launched his full-scale invasion of Ukraine in February 2022 - something NATO allies are only slowly starting to move towards.

Rishi Sunak said last week he would increase UK defence spending to 2.5% of national income by 2030 - claiming this equated to an additional £75bn in investment.

He also said he was putting the UK defence industry on a "war footing" and added £10bn of new funding would be dedicated to domestic munitions production over the next decade.

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'We need to build up our own stocks'

Asked how Britain could force defence companies like BAE Systems, Thales and Babcock - that have to answer to their shareholders, not the government - to increase production lines at the required rate and scale without some kind of legislation to force them to act, Lord Cameron revealed the plan for a new envoy for defence production.

"There is a specific munitions strategy of £10bn which will do exactly what you are talking about - the ramping up of production," he said.

"But crucially I think we can go further than that in terms of a specific defence envoy with the ability from the prime minister to go out and make sure we are doing those muti-year deals with the defence suppliers because we need not only to provide more weapons to Ukraine, we need to build up our own stocks.

"So this is very important, it is a national priority.

"The prime minister is giving the lead and I think the industry will respond."

Pushed on whether the new envoy - whose identity has not yet been revealed - would be the modern-day equivalent of someone like Lord Beaverbrook, who was tasked with expanding aircraft production during the Second World War, Lord Cameron said: "It is the 21st century so there won't be a Lord Beaverbrook."

But he signalled that the envoy's ability to approach industry with a commitment to fund multi-year contracts for munitions would be key - and could also drive down cost.

"It is possible to go to the defence contractors and say to them: 'You are not going to get the price you might have hoped for year after year after year because we are going to make a contract with you over the coming years to make sure we replenish our ammunition, our artillery, our long rage fires, our missiles' - those crucial things vital for Ukraine but also vital for our own defence."

As for why the government needed to appoint a specific envoy to this role, Lord Cameron said: "You need I think to have that direct line to the prime minister to make sure we are making this the national priority it clearly is."

Cameron warns of 'dangerous future'

Turning to the war in Ukraine, the foreign secretary said Europe faced "two futures" - one in which Ukrainian forces, backed by Western weapons, are able to push out the Russian invaders and secure what he called a "just peace".

"That is a footing on which you can see great security and prosperity for us and for Europe," he said.

But he warned: "A future in which Putin is successful and Ukraine is pushed back is I think a very dangerous future."

Nations such as Moldova and even the NATO states of the Baltics would be worried that President Putin might turn his attention towards them next, Lord Cameron said.

In addition, the authoritarian regimes in Iran and China would be watching closely.

"I think we are at an absolutely crucial tipping point in global affairs," Lord Cameron added.