The South African government yesterday denounced suggestions that it is using an alleged U.S. spy plot as a pretext for abandoning an American-backed plan to grant Namibia independence.

In a sharply worded statement issued here yesterday, South Africa's foreign minister, Roelof (Pik) Botha, assailed the insinuation by an unnamed American official as "false and reprehensible."

Botha said his government would continue to be guided in its decisions about Namibia, a South African-controlled territory with a predominantly black population, by the attitudes of "the democratic political parties representing the people of the territory."

Botha's statement on Namibia was prompted by remarks, reported in yesterday's editions of The Washington Post, by an American official, who asked not to be identified.

On Friday, the official sought to dismiss the spying charges as inconsequential and suggested that South African Prime Minister Pieter W. Botha's government "may have been positioning itself for rejection of the Namibia agreement by casting things in terms of a spy plot involving major U.S. government figures."

State Department spokesman Hodding Carter said last night that the United States would have no comment on Botha's statement. However, the American Official's suggestion of a linkage between Namibia and the spy charges is known to represent the continuing U.S. assessment of what is behind the Pretoria Government's actions.

South Africa's latest charges came in the wake of the State Department's refusal Friday to issue any apology for the alleged espionage activities by three U.S. military officials attached to the American embassy in South Africa.

The South African government on Thursday accused the three Americans of taking aerial photographs of secret installations from the embassy's official plane and ordered them expelled from the country. On Friday, the United States retaliated by ordering South Africa's two top-ranking defense attaches to leave Washington.

Responding to the American official's suggestion of a Namibia link in the matter, Foreign Minister Botha, who is not related to the prime minister, said:

"This allegation is false and reprehensible and is a comment not on my government but on the callousness of the unnamed official who suggested the linkage."

State Department officials refused Friday to deny publicly the spying allegations. Various official sources privately have confirmed that South African authorities had found an aerial camera aboard the U.S. embassy plane. There also have been reports from South Africa that allegedly unauthorized photos had been found.

Several U.S. officials have sought to downplay the charges by observing that U.S. spy satellites could obtain better pictures of military bases than what one called "a relatively primitive camera."

Responding to these observations in his statement issued by the South African embassy here, Foreign Minister Botha said:

"The implication is-if the reports are accurate-that the United States ought, because of its advanced technology, to be permitted to disregard diplomatic convention and allow its official representatives abroad to indulge in espionage. Such arrogance ill befits a democratic nation which professes moral pre-eminence."

Namibia, formerly Southwest Africa, is supposed to be moving toward independence under United Nations supervised elections. But progress has been halted, at least temporarily, by South Africa's charges that the U.N. plan will give an unfair advantage to insurgent forces that Pretoria alleges are communist-controlled.

The U.S. assessment that South Africa may be paving the way to repudiate the Namibia plan is prompted by the Botha government's tactics in making a noisy public outcry about the spy charges. In most Cases, U.S. sources have noted, governments that suspect another country's officials of espionage handle the situation quietly in order not to disrupt continuing relations.