ustralian Prime Minister Malcolm Fraser claimed yesterday that President Reagan had told him privately that he was much more critical of South African policies than he showed in his public policies and statements.

Fraser, who talked privately with Reagan for nearly two hours in the White House June 30, was defending his own policies against a strong attack from members of the ruling Liberal Party's right wing.

He has been stridently critical of South Africa's apartheid policies. Recently he attacked South Africa for delaying independence for Namibia and refused transit visas for the South African Springboks rugby team on its way to New Zealand.

At a meeting yesterday of Liberal Party members of Parliament, Fraser said he could reveal that Reagan had told him privately that he supported Fraser's views on South Africa. The Australian leader claimed that British Prime Minister Margaret Thatcher had also told him in private conversations that she also supported the Fraser views.

The issue has come to a head within the governing Liberal Party because of the imminence of the biennial meeting of the Commonwealth nations' leaders in Melbourne. The meeting starts Sept. 30. It is the first time the 44 members of the Commonwealth have ever met in Australia, and Fraser is promising to take a lead in toughening the Commonwealth's already substantially anti-South African policy.

Fraser has said he will support any Commonwealth move to apply international pressure to hasten the independence of Namibia.

He will also support Commonwealth principles, established at the London Commonwealth conference in 1977, to ban sporting contacts between Commonwealth countries and South Africa.

Two of the Commonwealth countries--Britain and Canada--are members of the five-nation "contact group" set up by the United Nations to discuss the independence of Namibia with South Africa. The others are the United States, France and West Germany.

Fraser has established strong links with the black African countries in the Commonwealth since, at the 1977 conference, he became the first conservative Australian prime minister to attack South Africa and its racially discriminatory policies of apartheid.

He was widely applauded by the black Africans at the last Commonwealth conference--Lusaka, Zambia, in 1979--when he took a leading part in formulating the agreement that led to independence for Zimbabwe and in convincing Thatcher to accept the agreement.

Under attack in his own party, Fraser argued as he has with increasing frequency in public that apartheid is "morally repellent."

He also argued that if equality were not granted in South Africa and independence granted to Namibia quickly, that people would resort even more to arms--which communist nations would supply.

Fraser's African policies have always caused him trouble in the Liberal Party--which despite its name, is akin to the right wing of the British Conservative Party.

Many members of his party see the white government and the white people of South Africa as the natural allies of virtually all-white Australia.