Chinese premier Wen Jiabao has warned the ruinous turmoil that engulfed the country in the past could re-emerge unless it tackles political reforms.
He also rebuked a populist fellow leader over a scandal that brought in-fighting among officials into public view.
In a three-hour news conference, his sole such event of the year, Mr Wen renewed a call for unspecified political reforms, particularly of the Communist Party leadership, saying that without them China's hard-won prosperity might fizzle.
No democratic firebrand, Mr Wen has issued similarly vague pleas before - and become a popular if lone voice among senior leaders by doing so. This time his tone was more emphatic, as was the setting.
The news conference was his last scheduled briefing before the 69-year-old steps down in a year after a decade in office. He said he is "seized by a strong sense of responsibility" to speak out and referred repeatedly to the judgment of history.
Corruption, the rich-poor gap and plummeting government credibility that beset China require institutional changes, he said.
To cap his plea, he made rare mention of the Cultural Revolution, 10 years of factional battles and radical egalitarianism that spiralled into violence in which millions were persecuted and many reform-minded leaders were jailed, sent into internal exile or left to die.
"Without successful political reform, it is impossible for us to fully institute economic system reform. The gains we have made in this area may also be lost," Mr Wen told reporters in the Great Hall of the People.
"New problems that have cropped up in China's society will not be fundamentally resolved and such historical tragedies as the Cultural Revolution may happen again."
The recurring references to the past and the wistful, reflective tone turned the premier's news conference into something of a swan song for the most popular member of the usually remote leadership.
Sometimes called "Grandpa Wen," he comes across as warm and caring. He has been shown eating dumplings with coal miners and consoling survivors of the devastating Sichuan earthquake and other disasters.
As the No. 3 in the party leadership who is primarily responsible for the economy, Mr Wen fielded a range of questions, from local government debt to currency reform. He offered Chinese funding of US infrastructure projects to create American jobs and rebalance lopsided economic ties with a crucial trading partner.
He sidestepped a question asking his views of the democratic uprisings in parts of the Arab world.
Mr Wen sounded resolute on government efforts to deflate a property bubble, saying "home prices in China are far from coming back to a reasonable level." The Shanghai and Shenzhen stock markets swooned, bucking the trend in markets elsewhere buoyed by strong Wall Street gains.
Mr Wen, President Hu Jintao and most of the leadership are stepping down following unwritten rules of succession and making way for younger leaders. The turnover always invites divisive infighting that the party prefers to keep under wraps.
That image of unity was ruptured last month by the cashiering of a top official in the mega-city of Chongqing who fled overnight to a US consulate, reportedly to seek political asylum.
Asked by a reporter about Deputy Mayor Wang Lijun's still unexplained fall, Mr Wen issued the harshest criticism to date of Chongqing party chief Bo Xilai, perhaps signalling the once-rising star is unlikely to be promoted to the uppermost ranks of power.
"The current party committee and the government of Chongqing must seriously reflect on the Wang Lijun incident and learn lessons from this incident," Mr Wen said.
While not mentioning Bo by name, Mr Wen once again delved into the past. He said the investigation into the scandal "should be able to stand the test of the law and history." He recalled the tortuous diversions into political campaigns that sidetracked China's climb from poverty to world power.
The comments seemed a swipe at Bo, who has promoted mass sing-alongs of communist anthems and other "red" culture that some see as worrisome preference of the extreme politics of the past.
Mr Wen was characteristically humble throughout his appearance as he looked back on his nine years as premier and 45 years in government service, since his start as a political instructor to geological survey teams in the poor inland province of Gansu.
"Due to my incompetent abilities and institutional and other factors, there is still much room for improvement in my work," Mr Wen said. "I should assume responsibility for the problems that have occurred in China's economy and society during my term in office for which I feel truly sorry."
Mr Wen appeared visibly slower, the pauses in his speech longer than in years past. Rumours within the diplomatic corps say he has been unwell for months, turning much of his workload over to Vice Premier Li Keqiang, his expected successor.
Mr Wen told reporters two years ago he liked to jog and swim to stay fit, though has little time for it, and he has been shown on state television playing basketball with Chinese high school students and baseball in Japan.