Former Japanese Prime Minister Tomiichi Murayama says the landmark 1995 war apology carrying his name is an international pledge that Japan must not change, amid speculation the current conservative leaders want to revise it.
Murayama said that Japan should also keep another apology over forced prostitution before and during World War II, and urged Prime Minister Shinzo Abe to stand by both statements.
''Nobody can deny the Murayama statement,'' he said during his rare public speech in Tokyo since his retirement in 2000.
''It has become an international pledge and Japan's national policy. It's impossible to deny it, and for that reason I trust Prime Minister Abe would observe it.''
The apology was issued under Murayama and was seen as Japan's main expression of remorse for its wartime and colonial past. It has since been endorsed by all 10 prime ministers, including Abe's earlier administration in 2007.
Since taking office in 2012, Abe has angered China and South Korea, which were occupied by Japan before and during World War II, by questioning the meaning of the word ''aggression'' in the 1995 apology and saying there is no international consensus on its definition. Abe suggested that his Cabinet does not necessarily support the entire apology, though he later promised to stand by it.
Abe's visit to Tokyo's shrine honouring the war dead including convicted war criminals in December has escalated tension with Japan's
Murayama was a Democratic Socialist who led the three-party coalition government that included Abe's Liberal Democratic Party from 1994 to 1996. He issued the statement of apology to mark the 50th anniversary of the end of World War II.
Murayama also criticised growing attempts by nationalist lawmakers to discredit the apology for forced prostitution by citing the lack of official wartime documents specifically stating that the government at the time systematically forced Asian women to provide sex for Japanese soldiers at military brothels.
Although numbers vary, historians say up to 200,000 women from across Asia, mostly Koreans, were forced into prostitution.
There is a growing movement by Japanese nationalists and revisionists to try to deny the use of coercion and scrap the 1993 apology signed by then-Chief Cabinet Secretary Yohei Kono.
They say the apology is based on false accounts provided by former sex slaves from South Korea.
Abe wants to issue a fresh statement marking the 70th anniversary of the end of World War II next year.
Since taking office for the second time, Abe has said he prefers to leave history up to historians and avoid comment.