The BBC on Sunday apologised to Japanese viewers over jokes about a man who survived both atomic bombs dropped on the country in World War II, following complaints from the embassy in London.
In the comedy television quiz show "QI", screened in Britain last month, panellists joked about the experience of Tsutomu Yamaguchi, who survived the bombings of Hiroshima and Nagasaki.
The British Broadcasting Corporation said it would be writing back to the Japanese embassy shortly.
Presenter Stephen Fry called Yamaguchi, who died last year aged 93, "the unluckiest man in the world".
He was on a business trip in Hiroshima on August 6, 1945 when the first bomb struck, leaving him with serious burns. The following day he returned by train to his home city of Nagasaki, which was bombed three days later.
He was the only man recognised by the Japanese government to have survived both.
Fry said: "Well, this man is either the unluckiest or the luckiest depending on which way you look at it."
Comedian Alan Davies, quipped; "bomb landed on him and bounced off?"
He later added: "He never got the train again, I tell you."
Fellow comedian Rob Brydon also chipped in: "Is the glass half empty, is it half full? Either way it's radioactive. So don't drink it."
Japanese viewers who took offence reportedly contacted diplomatic staff in London and emailed the BBC.
The broadcaster said it had received a letter from the Japanese embassy about "QI" and would be "replying to that shortly".
A spokesman added: "We are sorry for any offence caused.
"'QI' never sets out to cause offence with any of the people or subjects it covers.
"However, on this occasion, given the sensitivity of the subject matter for Japanese viewers, we understand why they did not feel it appropriate for inclusion in the programme."