Keir Starmer has condemned Vladimir Putin after he made it easier for Russia to launch nuclear weapons.

The Russian president signed a decree lowering the threshold at which the country’s military can use its deadly arsenal.

It is thought to be in direct response to Joe Biden giving Ukraine the go-ahead to use American long-range missiles on targets inside Russia.

Kremlin spokesman Dmitry Peskov said: “The use of western non-nuclear missiles by Kyiv against Russia, under the new doctrine, could provoke a nuclear response.”

He added: “Russia has always viewed nuclear weapons as a deterrent, the use of which is an extreme, forced measure.”

Asked about the move, a spokeswoman for the prime minister said: “It would be fair to say it’s the latest example of irresponsibility that we have seen from the depraved Russian government.”

At a press conference at the G20 in Rio de Janeiro on Tuesday, Starmer said: “There is irresponsible rhetoric coming from Russia and that is not going to deter our support for Ukraine.

“We’re now on day 1,000 of that conflict. That’s 1,000 days Russian aggression, 1,000 days of sacrifice in Ukraine.

“We have stood with Ukraine from the start and have been doubling down on my clear message that we must ensure that Ukraine has what is needed for as long as is needed to win this war against Putin.”

Earlier, Starmer refused to say whether the UK government will follow Biden’s lead by allowing Ukraine to use British-made Storm Shadow long-range missiles to attack Russia.

He said: “My position has always been that Ukraine must have what it needs for as long as it needs. Putin must not win this war. But look, forgive me, I’m not going to go into operational matters, because there’s only one winner if I do that, and that is Putin and it would undermine Ukrainian efforts.”