Tokyo, Japan (CNN) -- A leaked video is circulating in cyberspace, showing a boat collision that sparked a recent diplomatic battle between China and Japan.
The YouTube video shows the same collision that Japanese lawmakers watched on video last week, said legislator Hiroshi Kawauchi, of the ruling Democratic Party of Japan.
The Japanese Coast Guard shot the video, which is authentic and not doctored, said Kawauchi, who is a member of the House of Representatives in the Diet, Japan's legislature.
"The fact that the video was leaked is a big mistake for the government," he added. "It is totally different from presenting it to the public in an official manner, and it leads the people's further erosion of faith in Japan's government."
In September, Japan detained the crew of a Chinese fishing boat off disputed islands in the East China Sea. China calls the islands the Diaoyu; Japan calls them the Senkaku.
In response to the detainments, China made increasingly aggressive diplomatic threats. Beijing also halted ministerial-level talks with Tokyo, and both sides canceled trips to each other's nations.
Japan has since released the fishing crew, who China says were stopped illegally. Japan initially accused the captain of obstructing Japanese public officers while they performed duties. But authorities later said that releasing him was in the interest of maintaining relations with China.
The crash video that Japanese lawmakers saw has not been released to the public.
The video, posted on YouTube, shows what is thought to be the Chinese fishing trawler ramming into a ship, thought to be a Japanese Coast Guard vessel.
The Chinese government dismissed the video after Japanese lawmakers saw it, saying it had been edited and that it did not change the ownership of the islands.
On Friday, China's Assistant Minister of Foreign Affairs Cui Tiankai said: "I think the China-Japanese relationship has to overcome the current difficulties and move forward. This will serve the fundamental interests of both countries. So [we] hope [the] Japanese side will do everything possible to make sure that there's no further disruptions of the relationship."
The Chinese Embassy in Tokyo has contacted the office of Japanese Prime Minister Naoto Kan about the leaked video, making an "official inquiry," Kan's office said. No official protest was lodged.
Kan's office is investigating the leaking of the video, which has been shown on Japanese television.
The man apparently doing the videotaping says on the video that the date is September 7, 2010. That matches the detaining of the fishing crew.
The man also says on the video, in Japanese: "We've ordered them to stop, in Chinese language, but they didn't stop."
As the Chinese boat approaches, shouting is heard in Japanese. Unidentified voices shout: "Stop,stop!"
CNN's Jo Ling Kent contributed to this report.