President Carter told his senior staff and Cabinet "the shakedown cruise is over" in a "very tough" assessment of administration problems Sunday and yesterday, informed administration sources said last night.

"The president pointed out some mistakes he thinks he has made, but he made it damn clear that we've had 15 months now and the shakedown cruise is over," White House press secretary Jody Powell said.

The private talks at the presidential retreat were described by others as "the first time Carter has ever gotten tough with his people."

Carter, according to these sources, cited specific instances where Cabinet departments had not supported administration positions on legislation and where the White House staff had acted without giving the Cabinet members lead time to know what was going on.

Apparently reflecting his own recent conversations with members of Congress and such outside advisers as Atlanta lawyer Charles Kirbo, the president "worked over" the senior staff on Sunday afternoon, as one observer put it, and then had a "stiff" session with the Cabinet alone yesterday morning.

Later, the two groups joined to discuss the steps that might be taken to get on top of major policy problems and reverse the continuing decline in Carter's approval rating in the public opinion polls.

Carter reportedly reiterated confidence in all his Cabinet members and pledged that there would be no abandonment of "Cabinet government" in favor of a more centralized White House staff control.

But, officials said, additions and changes to the White House staff will be announced this week or next and Carter stressed to both Cabinet officials and his senior staff their accountability for the performance of their own offices and departments.

"He told us," one official said "that 'you hired your office. Either it works or it doesn't work.It's your job to see that it works.'"

"There was some talk," this source added, "that either people should shape up or ship out."

Cabinet officials and others in attendance were unusually guarded in their comments about the meeting but most suggested that it had cleared the air and brought a closer feeling of teamwork.

Carter reportedly "read the riot act" to both groups about leaks to the press critical of administration colleagues. "He said that if you're sore just bite your lip. Don't pop off to your staff and let them leak it to the press," one official said.

The meeting had been preceded by reports that Carter would abandon some of his reliance on Cabinet autonomy in favor of tighter, more centralized White House planning.

But Powell said, "This was not a process to abandon the concept of Cabinet government or to provide greater centralization of authority in the White House."

Specific steps to improve coordination of policy may have been discussed at Camp David, but officials willing to talk last night provided no details of those changes.

The White House and Cabinet officials, accompanied by Vice President Mondale, flew by helicopter to Camp David Sunday afternoon.

Sunday was spent relaxing and meeting in small, informal groups. Sunday night, the president and his wife, Rosalynn, hosted a reception for the officials before dinner.

Yesterday, Carter met alone with his Cabinet for an hour before inviting his White House advisers to join the group. Yesterday's meetings lasted from 8:45 a.m. to noon.

The President later told reporters that he had found the sessions "profitable, very helpful," asked if he would now do things differently, he said, "We'll do things better." Powell, who called the meetings "constructive and productive," said similar sessions will be held every few months.

Carter returned to the White House at 2 p.m. yesterday. He was accompanied by Mrs. Carter, Kirbo and Attorney General Griffin B. Bell.

Kirbo was the only person without an official position in the administration to attend the meetings, Powell said.