JOHANNESBURG, JAN. 25 -- Anthony Bloom, one of South Africa's leading white industrialists and the business establishment's most outspoken critic of apartheid, said today he is leaving South Africa to settle permanently in Britain.

Bloom cited "complex business, personal and family reasons" for his decision to leave South Africa and the business that his ancestors founded three generations ago after immigrating here from Lithuania.

Bloom said he remained critical of the timidity of South Africa's business community in attacking the government's apartheid policies, but he insisted in a news conference today that the "time trigger of my decision has been my family circumstances." He said a daughter who was seriously injured last year in a helicopter accident is still undergoing treatment in Britain.

His planned departure focused attention on a growing emigration problem in South Africa, in which a brain drain has been exacerbated by increasing numbers of professionals and management experts leaving for political reasons.

Bloom, 49, is chairman and chief executive officer of Premier Group Holdings Ltd., a huge conglomerate of food processing, manufacturing and pharmaceutical companies that has become part of the even larger Anglo American Corp.

He stunned the business world two years ago when he and a small group of white executives went to Lusaka, Zambia, to meet with leaders of the outlawed African National Congress in an attempt to open a dialogue with the black nationalist movement. The ANC is the main guerrilla force seeking to overthrow by force white minority rule in South Africa.

Bloom has repeatedly called for the release of imprisoned ANC leader Nelson Mandela as a prerequisite for negotiations between Pretoria and South Africa's 26-million black majority. He also has favored a system of one man, one vote, which the ruling National Party government has said it will never accept.

A year ago, Bloom said in an interview that despite his commitment to the cause of exerting pressure on the government for political reform in South Africa, he would have to consider emigrating for the purpose of assuring a future for his children. But he said then that he would not leave unless he considered the government's position to be hopelessly intractable.

Bloom, who has a law degree from Harvard and studied at Stanford, was never engaged deeply in partisan politics here. But he has been highly visible as an outspoken critic of the apartheid policies of the government of President Pieter W. Botha. He also has been a tireless advocate of dialogue between blacks and whites for the purpose of achieving a turnover of power.

The last major South African businessman to emigrate for stated political reasons was Gordon Waddell, chairman of Johannesburg Consolidated Investments Co., who left last year. Waddell was one of three people who controlled the giant Anglo American Corp.

White emigration from South Africa has gone up and down in the past two years, depending on the revolutionary climate. In 1986, a record number emigrated -- more than 1,000 a month, compared to 5,800 the previous year, according to the government's Central Statistics Services. These included 2,273 professional and technical workers.

Because of a general quieting of violence in the country's black townships the following year, the emigration rate in 1987 fell about 15 percent, according to the government.

White emigration during the peak 1984-86 period of revolutionary violence was popularly called the "chicken run," but emigration more recently has reflected cumulative frustration over South Africa's long-term economic and political future more than fear of an imminent political explosion.

A recent survey by the research firm Omnipoll said more than 160,000 white South African adults planned to leave in the next five years. There are 4.5 million whites in South Africa. The study showed that intention to leave was directly related to income: only 3 percent of those with a monthly household income under $1,250 said they want to emigrate, compared to 9 percent of those whose monthly incomes exceed $2,000.