Peter Lange, assistant professor of Government and an expert on Italian politics, argued last night on national television that Italian communists should be allowed to participate in a coalition government.

Appearing in a debate on "The Robert MacNeil Report," Lange cited the communists' "demonstrated ability to govern" in the five regional governments they control and their professed belief in democracy as reasons for his stand.

"The Italian communists have developed a doctrine of a route to communism that includes democracy," he said. "They're not acting on one global party doctrine."

Lange attributed the popularity of the Italian communists--who won 32 per cent of the vote in the last national election but remain unrepresented in the cabinet--to the failures of the recently dissolved coalition government and the Catholic Church's decline in power.

Marino de Medici, an Italian journalist and one of Lange's opponents in the debate, said last night he doubts whether NATO could survive in its present form if the communists gained more power in the Italian government.

Ray Kline, a former C.I.A. official now teaching at Georgetown University, also took issue with Lange's stand. Calling the $6 million the U.S. has given to the communists' rivals a "drop in the bucket," Kline said he opposes any improvement in relations with the communists.

Lange said that continued intransigence will only mean that rival parties will be less able to control the communists when they finally do gain representation in the cabinet.

But he said he does foresee some problems in sharing power with the communists, since the communists lack experience in national politics.