BEIJING — A group of retired Communist Party officials and intellectuals issued an unusually blunt demand on Tuesday for total press freedom in China, stating that the current climate of censorship and government control of the press violated China’s Constitution and debased the government’s claim to represent its citizens.

The document’s 23 signers, including academics and former executives of China’s state-controlled media, have no public influence on the nation’s ruling coalition of Communist leaders. Some of them have issued other public demands for reform in past years, to no effect.

Still, the baldness of their message — and its timing, coming days after the jailed intellectual Liu Xiaobo was awarded the Nobel Peace Prize and shortly before a major annual meeting of party officials — signaled that not all in the ruling establishment were content with the steadily tightening control over expression in the final years of President Hu Jintao’s and Prime Minister Wen Jiabao’s leadership.

Their letter’s unvarnished language was notable for including an undisguised attack on the legality of censorship by the party’s Central Propaganda Department, which ultimately controls much of what is published, broadcast or posted on the Internet here.

“This is an invisible black hand,” the signers wrote of the department, according to an English translation published by the China Media Project at the University of Hong Kong. “For their own reasons, they violate our Constitution, often ordering by telephone that the works of such and such a person cannot be published, or that such and such an event cannot be reported in the media. The officials who make the call do not leave their names, and the secrecy of the agents is protected, but you must heed their phone instructions.”

The writers’ “core demand,” they stated, was that China’s ineffectual legislature, the National People’s Congress, dismantle censorship procedures “in favor of a system of legal responsibility” for items that are freely published.

Some experts said that the demands, which were quickly squelched by censors after being posted on the Internet, were unlikely to have a serious impact on government policies.

“To the extent that people will learn about this letter, it resonates, because it shows there are different sensibilities within the party,” Nicholas Bequelin, a Hong Kong-based researcher for the advocacy group Human Rights Watch, said in an interview. “But it does not, on the political level, alter the balance.”

Although the open letter carries a date of this Monday, it is unclear whether the award of the Nobel Prize to Mr. Liu three days earlier had any influence on its content or release. Mr. Liu is not mentioned in the document, and in interviews, some of those involved with the letter said it had been largely written before the prize was announced.

It was primarily drafted by Xin Ziling, a onetime director of the editorial desk at the National Defense University of China, according to the wife of the most prominent signer, Mao’s former personal secretary, Li Rui. A second drafter was Tie Liu, editor of the privately published magazine Wangshi Weihen, or Scars of the Past, another signer, retired publisher Yu Haocheng, added.

Their motivation apparently was the case of a journalist, Xie Chaoping, who was arrested in August by Shaanxi Province police officers after publishing a book, “The Great Migration.” Among other things, the book documents years of forced relocations of local residents to build a dam in the 1950s, and accuses local officials of later embezzling funds meant to assist the relocation.

Mr. Xie’s case, which is referred to in the open letter, has become something of a rallying cry for press freedom among Chinese intellectuals. He was freed on bail last month.

The letter also refers to recent statements by Prime Minister Wen, including an interview with CNN, which suggest that the nation’s economic progress may be squandered unless the political system is further reformed. At one point, the letter notes that even those comments have been censored inside China, and that official reports on his remarks include only his statements on topics that do not involve reform.

“Of course, from our perspective the letter in a way is reacting to Premier Wen’s calls,” one signer, Jiang Ping, the former president of the China University of Political Science and Law, said in a telephone interview. “But whether the things we are calling for are consistent with what he has in mind, I don’t know.

“The reason I signed my name to this open letter is that it’s high time now we should have reform of the political system. The key element of this reform is freedom of speech, and I think now is the time to seek these reforms.”

Jonathan Ansfield and Li Bibo contributed reporting.