China's National Tourism Administration has ordered tour operators, agencies and tourists to boycott Japanese hotel chain APA after books claiming the 1937 Nanjing massacre never took place were left in rooms. The boycott could be potentially costly for APA as Chinese tourists spent an estimated $13bn (£10.3bn) in Japan in 2016, more than any other nationality.

The controversial book, written by APA's CEO Toshio Motoya, has been left in every room of the chain's 400 hotels. Motoya dismisses a number of generally accepted claims such as that up to 300,000 civilians were killed during the Japanese occupation of Nanjing. In an online statement, APA has defended the book as "freedom of speech" and said it will not be withdrawn from rooms.

"Although we acknowledge that historic interpretation and education vary among nations, please clearly understand that the book is not aimed to criticise any specific state or nation, but for the purpose of letting readers learn the fact-based true interpretation of modern history," says the statement.

"Therefore, we have no intention to withdraw this book from our guest rooms, no matter how many denounces [sic] may be made about it from whatever viewpoint. Japan constitutionally guarantees freedom of speech and no one-sided pressures could force any assertion made get repealed."

However China's National Tourism Administration calls the book an open provocation to Chinese tourists and has ordered visitors and Chinese companies not to use the chain. Spokesman Zhang Lizhong said: "We demand that all operators with international tours and online platforms completely stop all cooperation with this hotel."

Chinese Foreign Ministry Spokeswoman Hua Chunying joined the chorus of condemnation against APA. "To forget about history is betrayal, and to deny the guilt is doubling the crime," she said. "A small group of Japanese individuals are desperate to erase the historical crime. The more eager they are to do so, the more likely it will evoke people's memory of the past. These regressive behaviors have already triggered strong indignation of the Chinese people."

Japan has long been criticised for its reluctance to be candid about war crimes committed by its soldiers before and during World War II. Only recently did the country admit tp using "comfort women" during the war. Senior Japanese ministers also continue to visit the Yasukuni Shrine where notorious war criminals are honoured.