The relationship between the national press and the president has steadily deteriorated since the 1950s, Jody Powell, who was press secretary to former President Jimmy Carter, said yesterday.

Powell, who spoke yesterday at an Institute of Politics study group, said that negative press coverage has increased "independent of the personality or performance of the president."

Living in Sin

"The honeymoon" period, during which the press traditionally refrains from attacking the president, is necessary for a new Chief Executive "to get his feet on the ground," Powell stressed. He thinks, however, that the Carter administration was shortchanged, saying, "our honeymoon looked more like a one night stand."

On the other hand, Powell criticized the press for being too lenient with the Reagan administration. "The press must be careful not to let the president slip by. Reagan has been very successful at this." He pointed to Reagan's accelerated decontrol of oil prices as an issue he feels the press should have addressed in more detail.

Despite the generally negative atitude of the press, Carter would have improved his relationship with the media by getting to know White House correspondents, Powell said.

"Very few people in the press knew (Carter) when he was in Georgia, and its very difficult to make friends once you walk into that office," he added.

Powell said he signed a contract Tuesday for a book he will write on White House-press relations and on his experiences with the Carter administration, ministration.