Personal and ideological differences among black groups fighting apartheid in South Africa appear to have deepened during the last five years, undercutting the black protest movement's effectiveness.

The black consciousness movement has failed to recover from what amounted to a political lobotomy in October 1977, when authroties banned 18 organizations and jailed 50 of their leaders. Partly as a result, the movement is saddled with second-rate leaders and plagued by divisions. It is foundering as it attempts to define a cohesive philosophy of "liberation" and remains without effective grass-roots organization.

Even more crippling for any national black resistance to government policies is the bitter rivalry between the fractured black consciouness movement and Inkatha, the largest black political organization in the country led by Zulu chief Gatsha Buthelezi.

Inkatha's rapid organizational growth since 1976 -- burgeoning from 40,000 to more than 300,000 members, according to audited dues lists -- has combined with the frailty of the black consciousness movement and heavy police surveillance and harrassment to harden the lines between these two competing groups.

"The severity and bitterness of these conflicts have increased over the past two years," writes a South African pollster and sociologist, Lawrence Schlemmer.

The third major factor in South African black protest politics is the guerrila organizations: the African National Congress and, to a lesser extent, its rival, the Pan-Africanist Congress. But since both are banned, their sympathizers work underground or through other, overt organizations. As a movement, the African National Congress takes an ambivalent stance toward black consciousness and Inkatha, ranging from indifference to hostility.

South Africa's black population of about 20 million has always had -- and no doubt will continue to have -- various political persuasions and parties, given its ethnic and geographical differences.

But the failure of these three groups, particularly the two overt ones, to formulate common strategies is preventing a potentially stronger opposition to the government, even given the restrictive parameters allowed black politics in this country.

"It does make the liberation struggle much more difficult to get on an even keel," said one black journalist. "They spend so much energy fighting each other they have less time to fight the government."

For example, in early 1980 black consciousness activists in Soweto began a campaign to gather petitions calling on the government to release the jailed African National Congress leader Nelson Mandela. They did not ask Inkatha to help organize the campaign. Inkatha gave it only lukewarm support. Buthelezi publicly criticized it for hurting behind-the-scenes efforts he was making to get the government to release Mandela.

The lack of coordination probably limited the success of the campaign, which folded with less than 80,000 signatures.

In another area, Inkatha has set up a multiracial commission to study alternative constitutional models for South Africa. The black consciousness groups have not been invited to participate and they would refuse the invitation if they got one, they say. One prominent black regarded as a spokesman for black consciousness in Johannesburg told some whites that if they participate in the commission, he will not cooperate with them in the future.

The issues dividing Inkatha and the black consciousness movement relate to the role, if any, whites can play in blacks' emancipation, whether to negotiate with the government for incremental changes and the merits of socialism compared to free enterprise.

But the main dispute between the two groups concerns black political protest -- whether to work through the system or to refuse totally to collaborate and adopt confrontational although not necessarily violent tactics.

Buthelezi is chief minister of Kwazulu, one of the 10 rural reserves set up as political homelands for this country's black majority.He argues he has foiled the government's plans for Kwazulu because of his refusal to accept Pretoria-style "independence." Blacks cannot succeed in any mass protest action, Buthelezi says, until they first build up a government-created platform like Kwazula.

Black consciousness advocates say Buthelezi's collaboration with the homeland idea has given legitimacy to a system designed to keep blacks powerless and has exacerbated and institutionalized ethnic divisions among them.

"Some people preceive the struggle to be an ideological struggle and therefore are guided in their attitudes to the other groups on whether they subscribe to some ideological standpoint: if you're not with us, you're an enemy," retorted John Mavuso, an Inkatha official. "This is the basis cause of the conflict . . . which has paralyzed all efforts toward a united front of all organizations against apartheid, which is a pity.

"But we are not hamstrung by total adherence to a philosophy, an ideology. We don't talk system politics like the purists, who are holier-than-thous, who say we've dirtied ourselves by participation in the homelands. They are people responsible for the paralysis."

For their part, the black consciousness people accuse Buthelezi of being so sensitive to criticism and of having an overriding ego that he is unable to compromise or support anything that Inkatha does not initiate, direct and control completely.

At one point the rivalry was so intense that Nthato Motlana, head of Soweto's black consciousness-oriented Committee of 10, called Buthelizi a "traitor" and the Zulu chief called the Soweto physician a "political baboon." Publicly at least these exchanges have stopped.

The strife, along with disappointment that student unrest in 1976 failed to lead to an unstoppable momentum of black protest and that Prime Minister Pieter W. Botha's promises of change were more promise than change, have led to a discernible measure of hopelessness, confusion and apathy among many blacks.

"This country is change-resistant," said Mildred Mdladlanla, a middle-aged woman from Soweto. "Black opposition never wins. It has all the brainy people but it cannot win. All it has is the facts for the people. It cannot offer the people anything else."

Motlana admits glumly: "The government is achieving a measure of success with its homeland policy, which is gaining its own momentum."

But Schlemmer's research has corroborated what Buthelezi and black consciousness supporters do agree on: that there has been a "dramatic increase in discontent since 1977."