China has angrily rejected claims that the deaths of 300,000 Chinese civilians at the hands of Japanese troops in the Nanking massacre was a "big lie".
It is more embarrassment for Prime Minister Junichiro Koizumi
Senior Japanese politician Takami Eto made the suggestion while giving a speech in the west of Japan.
China's foreign ministry responded by saying there was "ironclad" evidence and any attempt to whitewash history would not succeed.
China has long contended that 300,000 people died in the Japanese occupation of the eastern city of Nanking, which is now known as Nanjing, in 1937.
Most historians say the figure is at least 150,000.
But nationalist Japanese politicians and academics say the figures have been inflated and some even question whether the massacre took place at all.
Senior conservative politicians regularly cause anger in China and South Korea by defending Japan's former wartime aggression.
In his speech on Saturday, Mr Eto also criticised past prime ministers for apologising for Japan's role in the war and making it appear that Japan was in the wrong, Kyodo news reported.
In response, China's Foreign Ministry spokesman Kong Quan said: "The Nanjing Massacre was a brutal crime committed by the Japanese militarists during their invasion war with China for which there is a mountain of ironclad evidence.
"The international community has already made its final
decision about this matter and any attempted plot to distort and deny historical facts cannot succeed," he said in a statement on the ministry website.
This is not the first time Mr Eto, a former cabinet minister of the governing Liberal Democratic Party, has sparked controversy.
In 1995, he resigned as head of the then Management and Coordination Agency after saying that Japan did "good things" during its 1910-45 rule of the Korean peninsula.
Correspondents say the comments will cause further embarrassment to the Prime Minister, Junichiro Koizumi, after a series of recent gaffes by members of his party:
- Yoshitada Konoike, state minister in charge of deregulation zones and disaster management, said the parents of a boy suspected of killing a small child should be beheaded.
- Former Prime Minister Yoshiro Mori said childless women should be denied welfare payments in old age.
- A former cabinet minister Seiichi Ota said at a debate on Japan's declining birth rate that at least gang rapists had a healthy appetite for sex.
- Chief Cabinet Secretary Yasuo Fukuda suggested that women who are raped are "asking for it" by the way they dress.