In a speech at the London Irish Centre ahead of St Patrick’s Day, Sir Keir said it was key to focus on the UK and Ireland’s “rich and long history”.
He said it was easy to see the relationship between the two countries “in narrow issues, the (Northern Ireland) Protocol at the moment”.
But he said the long partnership with the Republic, through Ireland’s ambassador to the UK Adrian O’Neill, was important.
Sir Keir said: “This relationship requires respect – equal respect – and understanding what it means to be a country.”
He added: “I think it tells us something about what’s going on in the world, particularly Ukraine, because at the heart of the conflict in Ukraine is a simple thing, the wish of a country to decide for itself its own future.”
“I didn’t think in my lifetime I would see Russian tanks rolling into a European country, soldiers kissing their children goodbye as they then stay to fight for their city and for the country, the awful bombing of hospitals. None of us thought we would see that.”
The Labour leader said behind those images was “that sense of democracy, of sovereignty, the right of a country to decide for itself on what it does”.
He added: “But when it comes to what does the UK stand for, what does Ireland stand for, when it comes to issues of sovereignty and self-determination, we stand together in the face of Russian aggression ...”
Sir Keir also said: “It is about the relationship between UK and Ireland, but it’s also about the way in which we view the world which is being challenged at the moment in a really profound way.”