Rishi Sunak has reportedly asked for a 'Goldman Sachs-style' audit of progress in the war in Ukraine, sparking fears he is moving towards a more cautious approach to Vladimir Putin's invasion.
Senior government figures are said be concerned the Prime Minister could change the UK's stance on the conflict as it enters a crucial phase.
A source in Whitehall compared the move to a 'Goldman Sachs dashboard' review of the invasion and Britain's supply lines to Ukraine.
Military chiefs have argued the next few months of the war, and the supply of weapons to help Ukraine fight it, will be essential.
Prime Minister Rishi Sunak has reportedly ordered an audit into Britain's supplies to the war in Ukraine
Russia and Ukraine have largely reached a stalemate in the south and east of Ukraine after almost a year since the invasion
Both Russia and Ukraine are in a stalemate in the south and east of the country, and Whitehall insiders argue Ukraine needs greater supplies in the next few months as Putin runs short of resources.
The source in Whitehall said: 'Wars aren't won [by dashboards]. Wars are won on instinct.
'At the start of this it was Boris sitting down and saying: "Let's just go for this." So Rishi needs to channel his inner Boris on foreign policy though not of course on anything else', according to BBC Newsnight.
A Downing Street source said it was not true that Sunak was being overly cautious and that 'the UK government's support for Ukraine is unwavering'.
They said the planned data-driven assessment would analyse the invasion and the importance of Britain's military supplies to Ukraine.
The source added: 'This is about looking at what we have put in, what we have got out.'
Russian President Vladimir Putin is said to be running low on resources for his invasion of Ukraine
Since Russian President Putin invaded Ukraine in February, the UK has one of the biggest suppliers of military resources to help battle the invasion.
The Whitehall source added that Ukrainian President Volodymyr Zelensky is aware of the change in approach by Downing Street and is trying to 'inspire' Mr Sunak to keep him on side during the conflict.
No 10 has insisted Mr Sunak is committed to supporting Ukraine in battling the Russian invasion.
A source close to the Prime Minister said: 'the UK government's support for Ukraine is unwavering'.
Mr Sunak recently travelled to Ukraine in a surprise visit to reaffirm the UK's support for the war-torn country.
He tweeted at the time: 'Britain knows what it means to fight for freedom.
'We are with you all the way.'