The daughter of one of the American hostages sent a letter to the Iranian president earlier this month, accusing the United States of "neocolonialism" and of violating the hostages' "human rights."

The letter, which stirred outrage among the families of several other hostages, was among developments that led to the formation of a group designed to represent the captives' families. The group is called Family Liaison Action Group, or FLAG, an acronym intentionally imbued with patriotic symbolism.

FLAG is the first formal organization established by families of the estimated 53 Americans held in Tehran since Nov. 4. Fifty Americans are hostages at the U.S. Embassy compound, and three others are confined at the Iranian Foreign Ministry, according to the State Department.

However, FLAG's leaders say they are unsure whether the new group will survive. "These things are not easy to organize," Louisa Kennedy, FLAG's new media representative and wife of a hostage, said in an interview yesterday. Her husband is economic and commercial officer Moorhead C. Kennedy Jr. "We may not be able to get it off the ground," she said.

Organizers of FLAG say they hope it will last long after the crisis has ended to provide emotional, psychological and practical assistance to the hostages and their families.

The letter that angered some hostages' families was sent by Luzette Graves to Iranian President Abol Hassan Bani-Sadr. Graves -- whose father, public affairs officer John E. Graves, is a hostage -- is a member of a family that recently called publicly for a congressional investigation of past U.S. actions in Iran and a public apology to Tehran.

Although Graves declined to make her letter public, the text was provided to The Washington Post by other sources. In it, she wrote, "We uphold that the human rights of our people were first and foremost violated by the U.S. government.

"The gist of many a country's foreign policy, neocolonialism, is a tacit violation of international law," she added. "We realize that the U.S. government, among others, committed such offenses in the past, and more particularly, in Iran throughout the ex-shah's regime."

Graves' letter irked other hostages' relatives not so much because of her language but because of her claim to speak for all the hostages and their families. She signed the letter, "For all my people."

Among those who sharply objected to Graves' letter was Ernest Cooke, whose son, Vice Consul Donald J. Cooke, is a captive. "That takes colossal nerve," he said in a recent interview. "I object strenuously to the rhetoric in the letter. It certainly does not present the political beliefs of the American people or of the hostages or of the hostages' families."

Kennedy said yesterday that the controversy over Graves' letter and other statements by the Graves family was a factor in the move to establish FLAG.

When FLAG emerged last weekend, however, it was embroiled in another controversy.

As FLAG's leaders prepared to announce the group's formation, it was disclosed that a letter from FLAG had been delivered to the White House, expressing objections to U.S. negotiations over medical treatment for the ousted shah of Iran, Mohammad Reza Pahlavi. The letter was said to have the support of 47 hostages' families.

The letter stirred another furor, partly because it was construed in some news reports as signaling a break with the Carter administration. One hostage's wife complained privately that FLAG already was becoming more political than she had hoped. "I couldn't go against my country," she said, referring to reports about the letter.

Louisa Kennedy said that the letter was meant to be private and that FLAG was designed "not to become political." She feared, she said, that FLAG may go "crashing down because of all this excessive publicity in the press."

FLAG, however, is intended as a patriotic self-help group. The American flag was chosen as its emblem for elaborate symbolic reasons, its leaders say. The 50 stars represent the 50 embassy hostages, the three colors represent the three Americans held at the Iranian Foreign Ministry and the 13 stripes stand for 13 other hostages released last November.

FLAG's efforts to help the hostages' families keep in touch with each other, discuss their emotional problems, exchange practical information and seek answers to questions about the Iran crisis are in line with psychologists' recommendations.

A State Department advisory group also recently urged such steps, saying they would result in "immeasurable benefits" for the families.

"You simply need to spend more time helping people, bolstering people -- I should say, helping ourselves," Louisa Kennedy said.