President Carter accused Sen. Edward M. Kennedy (D-Mass.) last night of damaging the national interest and the efforts to free the American hostages in Tehran by his critcism of the Iran and Afghanistan crises.

"The thrust of what Sen. Kennedy has said throughout the last few weeks is very damaging to our country and to the establishment of our principles and the maintenance of them, and to the achievement of our goals to keep the peace and get our hostages released," the president said in a nationally televised news conference.

Carter also accused Kennedy of making "false" and "erroneous" charges regarding the administration's efforts to gain the release of the American hostages in Tehran and to deal with the Soviet Union's invasion of Afghanistan.

The president's comments, a response to charges Kennedy made Tuesday in a speech at Harvard University, were another dramatic sign that the Democratic presidential race is growing more bitter by the day.

Earlier yesterday, White House press secretary Jody Powell described Kennedy's Harvard speech as "a disgraceful exhibition of political ambition that was unconstrained by either accuracy or responsibility."

Carter reacted most strongly to Kennedy's assertion that the administration had earlier rejected a U.N. proposal for a commission to hear Iranian grievances, possibly prolonging the captivity of the hostages, and a suggestion that the Afghan invasion might have been averted had the United States been more forceful in warning the Soviets.

"That is typical of what causes me the deepest concern," the president said. "First of all, his statements have not been accurate and they have not been responsible, they have not helped our country."

The violent White House reaction to Kennedy's increasingly sharper attacks on the president appeared to mark a turning point in the Democratic presidential race, converting it into the kind of bitter, party-splitting battle that Democratic officials have feared.

Powell set the stage for the news conference with his statement, and Carter clearly was primed to make his most serious charges of the campaign so far whenever the subject came up.

When he was asked about Kennedy's increasingly harsher attacks on his foreign policy, the president responded by accusing the senator of exceeding the "bounds of propriety and accuracy."

Asked if he feared the Democratic Party is headed for a damaging split because of the charges and countercharges, Carter said, "I didn't ask for a challenger," and then, ignoring the question, launched into a lengthy defense of his refusal to campaign openly or debate Kennedy.

"I look forward to the time when the hostages are released, when I can go out and campaign actively," he said. But until then, he added, "I will not assume business as usual as a partisan campaigner. . . ."

However, while the president said he would resume active campaigning once the hostages are released, he ducked a question on whether he would also debate Kennedy then, saying that will "have to be assessed in the future."

In a news conference in Dover, N.M., last night, Kennedy said Carter had "failed to understand" that his criticisms were leveled not at the country but at the president's handling of foreign and domestic policy.

Kennedy said he recalled "similar kinds of allegations and charges" when he and other senators criticized White House handling of foreign policy, and "another president -- President Nixon" tried to stifle the opposition.

"I would hope that this country has learned that lesson and learned it well," Kennedy said.

Throughout most of the Iranian crisis, the administration's public position has been to oppose establishment of any special commission to hear Iranian grievances unless the hostages are released first. In a speech at Georgetown University on Jan. 28, Kennedy called for the immediate establishment of a U.N. commission, but said it should not begin its work until the hostages are freed.

A variation of that proposal appears to hold the best prospect for a resolution of the crisis, and the essence of Kennedy's charge at Harvard was that the hostages might already be home had it been pursued earlier.

But administration officials said yesterday that such a plan has long been pursued and that Kennedy was told of it the weekend before the Georgetown speech, when he received private briefings from Secretary of State Cyrus R. Vance and U.S. Secretary-General Kurt Waldheim.

The dispute, in effect, came down to a question of whether Kennedy had sought to take credit for a proposal to end the crisis that he knew was already being considered by the administration.

Vance weighed into the fray yesterday with a statement issued for him by State Department spokesman Hodding Carter.

"Contrary to the senator's charge and as he knows, we have been working with the U.N. Secretary General for months on the possibility of creating an international commission that could lead to the release of the hostages," Vance said.

Saying that there were "numerous and serious misstatements" in Kennedy's speech, Vance also disputed Kennedy's charge that Carter failed to warn the Soviet Union against invading Afghanistan. Vance said the administration warned the Soviets "more than five times," and charged that Kennedy's opposition to the grain embargo against the Soviets and registration for the draft "indicates he still fails to recognize the seriousness of the Soviet action."

In Dover, N.H., where he was campaigning yesterday, Kennedy called Powell's statement "another attempt by the administration to stifle debate, to stifle constructive recommendations and suggestions by which the process of negotiation might move forward."

"I will not be silenced" he said.

"There was nothing in any briefing that I had that suggested they were prepared to formulate such a commission," Kennedy told an impromptu press conference in a classroom at a Plaistow, N.H. high school after he was informed of the White House charges.

Kennedy acknowledged that the idea of a commission "has been around for a long period of time," and added, "I am delighted that a commission established the way I have proposed it or others proposed it is going to be successful."

He said his only interest "is to see the hostages released. We've seen 102 days pass without the hostages being released. I say enough is enough."