Sir Keir Starmer has met Canadian Prime Minister Justin Trudeau during a trip to Montreal, in a visit that has seen him stress the importance of border security.
The Labour leader is in Canada for a summit of political leaders, as he seeks to burnish his image on the world stage.
Norway’s premier Jonas Gahr Store and Jacinda Ardern, former prime minister of New Zealand, are among the other leading names at the event for “progressive” politicians this weekend.
After the talks with Mr Trudeau, Sir Keir is expected to visit to Paris next week to meet French president Emmanuel Macron.
A Labour spokesperson said that Sir Keir and Mr Trudeau discussed “the moment is now for progressive governments, in response to the pace of change people across the world are facing”.
They added: “The two leaders discussed the opportunity presented by a transition to clean energy, for jobs, investment and the economy.
“They talked about the power of rules-based collaboration and the role of active, muscular centre-left governments in providing the answers to modern public challenges.”
The visit to Canada has seen the Labour leader push the importance of securing Britain’s borders, calling it an “acute security concern”.
He has also warned of the joint challenges that make up an “axis of instability” both in the UK and internationally.
Speaking at an event alongside the Norwegian prime minister, Sir Keir said: “In principle it’s wrong to think that control of the border is not a progressive issue.
“Because if you lose control of the border, a number of things happen – that’s when in certain places you get into the business of people talking about walls and fences because you’ve lost control of the border.
“It goes down this slippery slope. And if you can’t have a wall and a fence, you have some of the gimmicks that we’re seeing in the United Kingdom.”
The flurry of international engagements has been seen as a bid to appear statesmanlike and boost his leadership credentials ahead of a likely general election next year.
Labour officials are emphasising Sir Keir’s background as a director of public prosecutions in making the case that he could manage organised immigration crime if handed the keys to No 10.
No 10 appeared to downplay the significance of the Opposition leader’s expected Paris trip, saying it was “not unusual”.
Sir Keir could also be eyeing a White House meeting with US president Joe Biden in the coming months, whose “Bidenomics” and landmark green subsidy push has attracted admiration from Labour.
The trip to Canada also saw Sir Keir speak with former Bank of England governor Mark Carney, as well as former Swedish prime minister Magdalena Andersson.
Shadow foreign secretary David Lammy visited Montreal alongside his party leader, as he hit out at the current “ad hoc” relationship between the UK and EU and called for more regular formal meetings.
“We do think that UK relations with the European Union is our top priority. We can’t imagine describing, as Liz Truss did, Emmanuel Macron as an enemy,” Mr Lammy told The Observer.
“We think it is bizarre that the UK does not currently under this government have structured dialogue with the European Union in a constructive way.”
He added: “We don’t currently meet with the European Union to discuss mutual issues of concern, whether on a biannual basis or on a quarterly basis.
“At the moment there is nothing. It is all ad hoc. We have got to get back to structured dialogue.”