"The UK and allies are taking steps to bolster their security in the face of increased Russian threats," the statement said.

"Russia's actions put all of us at risk. As we give the Ukrainian people the support they need, we are also harnessing the breadth and depth of UK expertise to protect ourselves and our allies. This includes building the next generation of British warships," added Sunak.

The spending is the next phase in a programme under which three vessels are already under construction, and all eight frigates are expected to be completed by the mid-2030s, the statement said.

The announcement came with Sunak in Bali, Indonesia for a meeting of the Group of 20 that is expected to heap pressure on Russia over its invasion of Ukraine.

President Vladimir Putin has stayed away, instead sending his foreign minister, but Downing Street said Sunak and allies would "call out" the Russian leader's "callous disregard for human rights and stress that Russia's role in the international system will never be normalised while the war in Ukraine continues."