Yvette Cooper has vowed Britain stands “ready to act” after Donald Trump urged Nato countries to shoot down intruding Russian planes.
The foreign secretary criticised Moscow for its “provocative and reckless” violations of Nato airspace in recent weeks during a speech to the United Nations.
It came as Mr Trump said Ukraine can win back all territory it has lost to Russia – a dramatic shift from his previous call on Kyiv to make concessions.
Ms Cooper told the UN Security Council meeting on Tuesday: “Ukraine’s security is our security, and all of us depend on upholding the UN Charter.
“Russia’s actions seek to undermine democracy, secure conflict and spread instability far beyond Europe’s borders.
“In recent weeks, we’ve seen provocative and reckless violations of Nato airspace in Estonia, Poland and Romania, against which Nato stands firm, and we will be ready to act.”
Nato has said it will respond to Russian aerial incursions with “military and non-military tools”.
In a statement, the alliance condemned the incursion by three MiG-31 jets on Friday, describing it as “part of a wider pattern of increasingly irresponsible Russian behaviour”.
Nato warned: “Russia should be in no doubt: Nato and allies will employ, in accordance with international law, all necessary military and non-military tools to defend ourselves and deter all threats from all directions.”
On Tuesday evening, former prime minister Boris Johnson said the UK and its allies lack “the will and the leadership and the sense of urgency” to do more to help Ukraine.
Speaking at the opening of an exhibition on Ukraine, he asked why frozen Russian assets are still not being used to fund the war effort, why the UK is still buying uranium from Russia, why it has not sanctioned Russian energy company Rosneft and why it has not imposed secondary sanctions on those still buying hydrocarbons from Russia.
Mr Johnson said: “I’ll tell you why. It’s because we’re still apprehensive about the consequences, and because we still fundamentally lack the will and the leadership and the sense of urgency to get this done.”
