The end today of a sixth-month effort by Commonwealth leaders to promote a peaceful settlement of South Africa's racial conflict is likely to lead to an increase in pressure on Britain to agree to economic sanctions against Pretoria.

In a final meeting here today, the seven-member Eminent Persons Group completed a report on its efforts, due to be distributed next week to Commonwealth heads of state and then made public.

The South African government said Saturday it was studying proposals from the Commonwealth group, even though the group announced it was ending its initiative, The Associated Press reported from Cape Town.

The group was created during the last Commonwealth summit, held in Nassau, Bahamas, last fall, as a compromise between Prime Minister Margaret Thatcher, who consistently has opposed sanctions, and the rest of the 49-member organization of Britain and some of its former colonies, which favors them.

Led by Australian former prime minister Malcolm Fraser and Nigerian former head of state Olusegun Obasanjo, the group's mandate was to "initiate, in the context of a suspension of violence on all sides, a process of dialogue across the lines of color, politics and religion, with a view to establishing a nonracial and representative government."

Its mandate originally was to last at least until August. But the group suspended its efforts following last month's South African military raids against Zimbabwe, Botswana and Zambia.

According to a report in The Times of London today, the group has written a letter to South African authorities saying that it sees "no merit in further discussions" in the absence of movement toward two of its principal goals -- the freeing of imprisoned African National Congress leader Nelson Mandela, and the lifting of a ban against the ANC.

It is not known whether the group's final report recommends that economic sanctions be imposed against the Pretoria government. But even if it leaves the question open, the apparent failure of its overall mission will serve to increase pressure on Thatcher from both her domestic critics and Commonwealth colleagues.

Criticism of Britain's isolated position on sanctions stepped up markedly within days of the South African air and ground attacks against alleged ANC bases in neighboring African countries last month. In a heated session in Parliament, Thatcher "totally and utterly" condemned the raids, but she insisted that "sanctions would not help to achieve the objectives that we seek."

But in addition to sharp criticism from her domestic political opposition, and restive feelings within her own Conservative Party, Thatcher reportedly has been pressed on sanctions by Queen Elizabeth II, who takes very seriously her role as head of the Commonwealth and chief unifying force within the organization.

Several press reports here over the past month have said that the queen is increasingly concerned about the deterioration of the situation in South Africa and Britain's isolation. Thatcher's office yesterday repeated a standard policy of refusing to comment on "private conversations" between the prime minister and the queen.

Commonwealth Secretary General Shridath Ramphal has made his dissatisfaction with Thatcher's position increasingly public. Late last month he warned that "those who, for ideological or other reasons, believe that sanctions may not work, must themselves be helped to recognize that sanctions represent the course of conduct most likely to help the process of peaceful change."

Zambian President Kenneth Kaunda has threatened to withdraw from the Commonwealth and said in a recent interview with The Observer newspaper here that he had had similar "representations" from Commonwealth colleagues. Accusing the British government of openly supporting apartheid, Kaunda said he found Thatcher's position "morally and politically unacceptable."