The Soviet Communist Party newspaper Pravda today accused U.S. Ambassador Malcolm Toon of slandering the Soviet state the sharpest public attack on an American envoy here in years.

The article sharply criticized a speech Toon made in Atlanta. Ga., earlier this week according to Radio Moscow. Toon has been on a speaking tour of U.S. cities for the past few weeks and his comments on the Soviet Union as reported in the press here have at times been caustic.

Pravade said Toon dwelt on the alleged racist nature of Soviet society, on microware radiation directed at the U.S. Embassy in Moscow and about Soviet fears of China.

It said the ambassador was behaving extremely "undiplomaticly" by slandering the state whose hospitality he enjoyed according to a Moscow Radio account of the Pravda article. Such actions, the paper said, cannot contribute to better relations between the United States and the Soviet Union.

Suggesting that Toon's speech in Atlanta did not do him credit as an ambassador, Pravda also made reference to Toon's expression of dissatisfaction with internal Soviet legal proceedings apparently a reference to recent dissident trials and legal actions against Americans in the Soviet Union.

In Washington, U.S. officials promptly dismissed Soviet charges as a "cheap shot" at the ambassador. They suggested that if the article's goal was to have the Carter administrations replace Toon with another envoy, was likely to have the opposite effect.

Toon, 62, a tough-talking career diplomat in his Atlanta speech discussed Soviet-American relations, the Middle East, Moscow's policy in Africa and the strategic arms limitation talks.

Speaking about Soviet involvement in Africa and their use of Cuban troops, Toon suggested that Moscow's influence in Africa would be shortlived.

"The Soviet Union is a highly racist society," Toon said. "Certainly the Africans understand this as well as I do. So in the long ran I don't think there will be any substantial (Soviet) presence on the continent of Africa.

Toon was appointed ambassador to Moscow in 1976, after serving as ambassador to Irael. Yugoslavia, and Cnechoslovakia. The Russians for three months delayed accepting Toon's appointment and he arrived in Moscow in January 1977.

There was some discussion here when President Carter took office that the new Democratic administration would select its own candidate for the Moscow post. But after several weeks of confusion, Toon's name was resubmitted.