Sir Keir Starmer will visit British troops serving in Estonia to reaffirm Labour’s “unshakeable commitment to Nato”, his spokesman said.
The opposition leader is due to travel to Nato’s eastern flank with shadow defence secretary John Healey on Wednesday to speak with British armed forces deployed at the Tapa military base, where they are serving as part of Nato’s Enhanced Forward Presence.
Prime Minister Boris Johnson last week made the same journey to the country, which shares a border with Russia.
A spokesman for Sir Keir said the UK Government has Labour’s “full support” for boosting Britain’s presence in eastern Europe following Moscow’s invasion of Ukraine.
“Labour has been clear in our support for the security of Nato allies, particularly in the face of Russian aggression in Ukraine,” a spokesman told reporters.
“Labour’s view is that we should bolster and enforce our Nato allies, especially on the eastern flank, and the Government has our full support in the work it has been doing to do that.”
Speaking in the House of Commons, Mr Healey said Russian President Vladimir Putin had “miscalculated on the international resolve to isolate Russia” and “on the strength of Western and Nato unity”.
The shadow cabinet member drew comparisons to the September 11 2001 World Trade Centre attack, urging ministers to “respond to new threats” in a similar way that the New Labour administration did more than 20 years ago.
He went on: “Our Labour commitment to Nato is unshakable and the Government again has our full support for reinforcing Nato nations on the alliance’s eastern border with Russia.
“The Labour leader and I fly out tonight to Tallinn to reassure Estonia of the united UK determination to defend their security and to thank our British forces deployed there from the Royal Tank Regiment and the Royal Welsh Battlegroup.”
Ukrainian President Volodymyr Zelensky renewed his call for the West to police his country’s skies against Russian air threats during an impassioned speech to MPs on Tuesday.
But Sir Keir’s spokesman said he does not support implementing a no-fly zone over Ukraine – a view in line with the UK Government and other Nato allies.
The party also appeared coy on backing a bid by Poland to handover fighter jets to Ukrainian pilots.
The US has said Warsaw’s offer to give its MiG-29 planes to Washington so they can be passed to Kyiv raises serious concerns for the Nato alliance and the plan is not “a tenable one”.
Asked whether Sir Keir supported the Polish offer, his spokesman said: “People will be aware there is a distinction between providing defence equipment – that we fully support – and other questions that have been raised by some of the other proposals, such as the no-fly zone.
“But ultimately these are decisions for Nato to make collectively.”
Told that no collective decision had been made but that Washington had effectively ruled out the idea, the spokesman replied: “I think that equates to the same outcome.”