Vladimir Putin put Russia’s nuclear deterrent on high alert after “absolutely unacceptable” remarks by Liz Truss, according to the Kremlin.
But Downing Street said the claim was “designed to distract from the situation on the ground” as Russian troops face stiff resistance from Ukraine’s forces.
Moscow put its nuclear forces on a “special regime of combat duty” on Sunday.
Kremlin spokesman Dmitry Peskov went further on Monday and blamed the decision to escalate tensions on Truss.
“Statements were made by various representatives at various levels on possible altercations or even collisions and clashes between Nato and Russia,” he told a press briefing, the Interfax news agency reported.
“We believe that such statements are absolutely unacceptable. I would not call the authors of these statements by name, although it was the British foreign minister.”
It was not immediately clear what statements the Kremlin was referring to.
On Sunday, Truss suggested the UK government would “absolutely” support Brits who wanted to travel to Ukraine to fight Russian forces.
No.10 has distanced itself from the comment and said British nationals should stay away from the conflict.
The foreign secretary also warned: “If we don’t stop Putin in Ukraine, we are going to see others under threat: the Baltics, Poland, Moldova, and it could end up in a conflict with Nato. We do not want to go there.”
In response to the Kremlin’s comment about Truss, Boris Johnson’s spokesperson said the “rhetoric we are seeing from Putin’s regime” was “designed to distract from the situation on the ground”.
The prime minister has also dismissed the nuclear alert itself as a “distraction” from the struggle Russian troops are facing.
Earlier, Ben Wallace, the defence secretary, said his 12-year-old son had called him worried about the step, as he downplayed the threat’s significance.
“We don’t see or recognise in the sort of phrase or the status he described as anything that is a change to what they have currently as their nuclear posture,” he told BBC Breakfast.
“This is predominantly about Putin putting it on the table just to remind people, remind the world, that he has a deterrent.
“We will not do anything to escalate in that area, we will not do anything to feed any miscalculation, we take it very, very seriously.
“But at the moment this is a battle of rhetoric that President Putin is deploying, and we just have to make sure we manage it properly.”