Mr Johnson visited Rwanda and talked up the UK's free trade credentials, stressing the "shared sense of mutual trust" among states.
He said he had spoken to the Rwandan president about the UK’s controversial asylum policy, noting: “I just had a great talk with Paul Kagame.
“He cares passionately about this. He has himself been a refugee for a long time. He knows what it is like.
"He sees the problem of vulnerable people being trafficked across the Channel and being trafficked around the world.
“He sees this as an opportunity to fix what is an increasing global problem, by a partnership between the UK and Rwanda. It is not just about migration."
He continued: “It is about education, it is about trade, it is about all sorts of things, it is about green technology, financial services, all sorts of areas. It is a partnership that is growing.”
To critics of the policy, Mr Johnson accused them of basing their concerns on “a perception, perhaps a stereotype of Rwanda that is now outdated”.
Referring to train strikes currently ongoing in the UK, he said: “To have a great future for rail, for railway workers and their families, we have got to have some sensible reforms and that is things like reforming ticket offices – I did a huge amount of that when I was running London.
“It is stuff that maybe the union barons are more attached to perhaps than their workers. I think the strikes are a terrible idea."
Earlier, a Downing Street Spokesperson said: “The Prime Minister met Rwanda’s President Paul Kagame this morning, in his first engagement in Kigali ahead of the Commonwealth Heads of Government Meeting.
“He congratulated President Kagame on Rwanda’s extraordinary social and economic development in just a few decades, noting how pleased he was to be in the beautiful city of Kigali.
“The Prime Minister welcomed Rwanda’s moral stance on the war in Ukraine and the leaders discussed ways to address the international fallout from Putin’s invasion – including sharply rising global food prices, which are hitting African countries the hardest.
“The leaders also praised the successful UK-Rwanda Migration and Economic Development Partnership, which is tackling dangerous smuggling gangs while offering people a chance to build a new life in a safe country.
“As the UK hands over the Commonwealth Chair-in-Office to Rwanda, the Prime Minister said he hopes CHOGM is a great success.
"The Prime Minister and President Kagame agreed that the Commonwealth is a unique forum to address pressing global challenges and that the Summit should be a demonstration of unity and progress.”
Mr Johnson made his speech in Rwanda
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The PM defended the UK's migrant policy on the trip
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