Russia has suffered its worst ever month for casualties since the start of the war in Ukraine, the UK chief of defence staff has told the BBC.

Admiral Sir Tony Radakin said Russia’s forces suffered an average of about 1,500 dead and injured “every single day” in October, bringing its losses to 700,000 since the war began in February 2022.

Russia does not disclose the number of its war dead, but Western defence officials have said October’s death toll was the heaviest so far.

In an interview with BBC One’s Sunday with Laura Kuenssberg programme, Sir Tony said the Russian people were paying an “extraordinary price” for Putin’s invasion.

“Russia is about to suffer 700,000 people killed or wounded – the enormous pain and suffering that the Russian nation is having to bear because of Putin’s ambition,” said Sir Tony.

He said the losses were for “for tiny increments of land”.

“There is no doubt that Russia is making tactical, territorial gains and that is putting pressure on Ukraine,” he said.

But he added that Russia is spending more than 40% of its public expenditure on defence and security, which he said was “an enormous drain” on the country.

While allies of US President-elect Donald Trump insist that Ukrainian President Volodymyr Zelensky may have to cede territory to bring the conflict to an end, Sir Tony insisted that Western allies would be resolute for “as long as it takes”.

“That’s the message President Putin has to absorb and the reassurance for President Zelensky,” he told the programme.

Trump has consistently said his priority is to end the war and stem what he characterises as a drain on US resources, in the form of military aid and financial support to Ukraine.

But he has yet to divulge how he intends to do so – and will likely be hearing competing visions for Ukraine’s future from his various advisers.

Earlier this week, Putin congratulated Trump on his election victory and said Trump’s claim that he can help end the war in Ukraine “deserves attention at least”.

Trump’s Democratic opponents have accused him of cosying up to Russian President Vladimir Putin and say his approach to the war amounts to surrender for Ukraine that will endanger all of Europe.

Bryan Lanza, a Trump political adviser during his 2016 and 2024 campaigns, has said the incoming administration will focus on achieving peace in Ukraine rather than enabling the country to gain back territory occupied by Russia.

Mr Lanza told the BBC the incoming administration would ask President Zelensky for his version of a “realistic vision for peace”.

A spokesperson for Trump distanced the incoming president from the remarks, saying Mr Lanza “does not speak for him”.

Last month, Zelensky presented a “victory plan” to the Ukrainian parliament that included a refusal to cede Ukraine’s territories and sovereignty.

The Kremlin dismissed the plan with a spokesman saying Kyiv needed to “sober up”.