Sir Keir Starmer has been urged to allow Ukraine to use British-made Storm Shadow long-range missiles inside Russia.
Shadow defence secretary James Cartlidge welcomed the US giving Ukraine permission to use their long-range missiles inside Russia.
The Tory frontbencher said he hoped the decision by outgoing US President Joe Biden would pave the way for the UK to follow suit.
He told Sky News: “I welcome it very strongly. I think it’s important, and I hope it is a precursor to the UK granting full autonomy on use of Storm Shadow (missiles).”
The shadow defence secretary said it was “the right time” for permission to be granted for the weapons and said the Conservatives had been calling for the move since the summer.
He added: “Obviously these are complex matters. On this we had to move with the Americans, so I welcome the fact that the President has given this steer, and I hope it now leads to the UK doing the same.”
Mr Biden’s decision comes after months of pressure from Ukrainian President Volodymyr Zelensky.
It could see long-range missiles used initially in the Kursk region, where Ukrainian troops have launched an incursion into Russian territory and Vladimir Putin has bolstered his defences with troops from North Korea.
The UK Government has been reluctant to give Ukraine permission without a shift in US policy, in part because the missiles use American navigation data.
Mr Zelensky has been lobbying Western allies for permission to strike targets within Russian territory, arguing that he is effectively being forced to fight with his hands tied because he cannot hit the bases Mr Putin is using to launch air attacks against his country.
The Ukrainian leader said “long-range capabilities” were a key part of his “victory plan”.
“There’s been much said in the media today that we have received approval to take relative actions,” he said.
“But strikes are not carried out with words. These things are not announced. The missiles will speak for themselves.”
There has been no response from No 10 yet to Mr Biden’s decision, which has not been officially announced but has been widely reported in the US.
But Sir Keir Starmer said “we need to double down” on support for Ukraine and the issue was “top” of his agenda at this week’s G20 summit of world leaders in Brazil.
