HO CHI MINH CITY, Vietnam -- His bookshelves are filled with the collected works of Marx, Engels and Ho Chi Minh, the hallmarks of a loyal career in the Communist Party, but Nguyen Phuoc Tuong, 77, says he is no longer a believer. A former adviser to two prime ministers, Mr. Tuong, like so many people in Vietnam today, is speaking out forcefully against the government.
"Our system now is the totalitarian rule of one party," he said in an interview at his apartment on the outskirts of Ho Chi Minh City. "I come from within the system -- I understand all its flaws, all its shortcomings, all its degradation," he said. "If the system is not fixed, it will collapse on its own."
The party that triumphed over American-backed South Vietnamese forces in 1975 is facing rising anger over a slumping economy and is rived by disputes pitting traditionalists who want to maintain the country's guiding socialist principles and a monopoly on power against those calling for a more pluralist system and the full embrace of capitalism.
Perhaps most important, the party is struggling to reckon with a society that is better informed and more critical because of news and opinion that spread through the Internet, circumventing the state-controlled news media.
Since unifying the country 38 years ago, the Communist Party has been tested by conflicts with China and Cambodia, financial crises and internal rifts. The difference today, according to Carlyle A. Thayer, one of the leading foreign scholars of Vietnam, is that criticism of the leadership "has exploded across the society."
In an otherwise authoritarian environment, divisions in the party have actually helped encourage free speech because factions are eager to tarnish one another, Dr. Thayer said.
"There's a contradiction in Vietnam," he said. "Dissent is flourishing, but at the same time, so is repression."
As dissident voices have multiplied among Vietnam's 92 million people, the government has tried to crack down. Courts have sentenced numerous bloggers, journalists and activists to prison, yet criticism, especially online, continues seemingly unabated. The government blocks certain Internet sites, but many Vietnamese use software or Web sites to maneuver around the censorship.
"Many more people are trying to express themselves than before, criticizing the government," said Truong Huy San, an author, journalist and well-known blogger. "And what they are saying is much more severe."
Mr. San, who is on a fellowship at Harvard, is the author of "The Winning Side," perhaps the first critical, comprehensive history of Vietnam since 1975 by someone inside the country. Widely read in Vietnam, the two-volume work, written under the pen name Huy Duc, was printed without a permit from the government and describes such acts as the purges of disloyal party members and the seizure of south Vietnamese business owners' assets.
For casual visitors to Vietnam, surface evidence of economic progress may make it hard to understand the deep pessimism that many express in the country. Millions of people who a decade ago had only bicycles now speed around on motor scooters past factories and office towers.
The economy blossomed in the 1990s after reforms gave birth to Vietnam's awkward mix of a market economy closely chaperoned by the Communist Party. Even now, the Vietnamese economy is still projected to grow at about 4 percent to 5 percent this year, thanks in part to strong exports of rice, coffee and other agricultural products.
But the real estate market is frozen by overcapacity, banks are saddled with bad loans, newspapers are running articles about rising unemployment, and the country is ranked among some of the world's most corrupt by Transparency International, a global corruption monitor. (The country ranks 123rd on a list of 176, in which those with low numbers are the least corrupt.)
Vietnamese business people complain of overbearing government regulations imposed by a party that believes it can be the vanguard of capitalist enterprises.
And many say that Vietnam is directionless, despite its seemingly irrepressible industriousness and youthful population.
"In my 21 years here I've never seen this level of disenchantment with the system among the intelligentsia and entrepreneurs," said Peter R. Ryder, the chief executive of Indochina Capital, an investment company in Vietnam. "There's very meaningful debate within the business community and within the party -- people who are superconcerned about the direction that the country is going."
At the Spring Economic Forum, a conference held in early April that is organized by the economic committee of the National Assembly, participants "were fighting to have a chance at the microphone," according to Le Dang Doanh, a leading economist who attended the forum, which he described as "stormy."
He said there was widespread criticism that although the economy needed profound restructuring, "almost nothing has been implemented."
"It's a crisis of trust," Mr. Doanh said. "Better times have been promised every year, but people don't see it."
At the center of the political storm is Prime Minister Nguyen Tan Dung, who has been in power since 2006. Mr. Dung's brash style and ambitious program for the economy initially won him supporters because he broke from the mold of the stodgy party apparatchik.
But he alienated many party members by dismantling an advisory board that had been a leading force behind the reform program (and that board included Mr. Tuong, the Marxist scholar, among many other senior party members).
More important, Mr. Dung's trademark policy, his forceful push to build up state-run companies along the lines of South Korea's private conglomerates, backfired.
Run by executives with close ties to the Communist Party hierarchy, the enterprises expanded into many businesses they were unqualified to manage, economists say, and speculated in the stock market and in real estate. Two of the largest state enterprises nearly collapsed and remain close to insolvency.
Mr. Tuong, the Marxist scholar, says the tensions in the Communist Party have been heightened by the troubles with the economy.
In February, he helped write an open letter to the party's general secretary, Nguyen Phu Trong, urging changes to the country's Constitution that would "ensure that real power belongs to the people." He has yet to receive a response.
Mr. Tuong says he has been eager to promote change since his days as adviser to Prime Minister Vo Van Kiet, who helped overhaul the economy in the 1990s.
But today he feels the pressure of time. He has cancer, though it appears to be in remission, and he talks about the disease as a sort of intellectual liberation spurring him to tell what he now views as the truth.
"In a nutshell, Marx is a great thinker," he said. "But if we never had Marx it would have been even better."
This article originally appeared in The New York Times.