Keir Starmer has accused Vladimir Putin of plumbing “new depths of depravity” as speculation mounts that the UK will give Ukraine the go-ahead to fire long-range missiles into Russia.

US president Joe Biden has reportedly approved the use of American rockets with a range of 190 miles to be used by Kyiv as part of the ongoing war.

Starmer has previously given his backing to Ukraine using UK-built Storm Shadow missiles, but it was always understood that the White House would need to give its approval first.

A spokeswoman for the PM today said she would not “comment on operational matters”, but she added: “We’ve always said we want to make sure Ukraine is in the strongest possible position going into the winter to defend its sovereign territory.

“In recent days we have seen Putin reach new depths of depravity, systematically attacking infrastructure, depriving families of warmth and light, killing civilians through drone missile attacks as part of his ongoing illegal war.

“As the prime minister said, it’s important we double down and that Ukraine is provided with the support it needs for as long as it needs. Our support for Ukraine is iron clad and will continue on that basis.”