Boris Johnson's shirt hanged out the back of his trousers as he talked to Prince Charles

British Prime Minister Boris Johnson and his wife Carrie Johnson attended a dinner with Prince Charles, the Duchess of Cornwall, and other Commonwealth leaders here in Kigali, Rwanda.

Senior journalist Richard Palmer who accompanied the royal couple on the tour said, "The prime minister’s shirt was hanging out the back of his trousers as he and his wife Carrie chatted to the Prince of Wales and Duchess of Cornwall before the dinner.

Johnson met with Prince Charles in Kigali on Friday on the sidelines of a meeting of Commonwealth leaders, after media reports the heir to the throne privately described the government's plans to send asylum seekers to Rwanda as "appalling"

Earlier this month two British newspapers reported that Charles had privately criticised the plans. Charles was concerned the controversial asylum policy would overshadow the Commonwealth meeting where he is representing his mother Queen Elizabeth, The Times said.

The government says the deal will stem the flow of dangerous cross-Channel trips and smash the business model of people-smuggling networks.

Asked about Charles' purported comment, Johnson said: "I have no evidence for the assertion that you made ... I can’t confirm that. I think the policy is sensible, measured."

"I very much look forward to seeing (Charles)... but you would not expect me to comment on conversations that I may or may not have with him."