THE survival of a tribe of Brazilian Indians is under threat following revelations that its women have been subjected to mass sterilisation by a politician seeking to win votes for next month's general election.

Sixty-three women from the dwindling Pataxó Hã hã hãe tribe of the north-eastern state of Bahia were allegedly tricked into being sterilised by Roland Lavigne, who is also a doctor.

He apparently offered the operations in exchange for Indian votes. The women opted for sterilisation because of a lack of alternative birth control under a flagging public health system. "With every election we have an epidemic of sterilisations," said Ana Maria Costa, a doctor specialising in reproductive rights.

The mass surgery is also believed to have won approval from the local fazendeiros (farmers), who have long been in conflict with the tribespeople over land and would like to see them wiped out.

The Brazilian authorities have now launched an investigation, and the scandal looks likely to provoke an international outcry similar to that over the mistreatment of the Yanomami Indians in the Eighties.

The Washington-based Centre for Justice and International Law says it has "serious concerns" and is considering reporting Brazil to the United Nations Commission on Human Rights.

"This is genocide," said Roberto Liebgott, of the Missionary Council for Indigenous Affairs, which is carrying out a survey of the 1,500-strong Pataxó community. "It was a deliberate attempt to wipe out an entire tribe."

In some villages, such as Baheta, in southern Bahia, every woman of child-bearing age was sterilised, putting at risk the whole future of the community. Wilson Ninho, a village chief, said: "The fazendeiros tried to get rid of us through intimidation and gunfire and now they are using sterilisation."

The revelations have emerged as campaigning continues for elections on October 4. While it is common practice in developing countries to offer incentives for votes - such as bicycles, food or money - Brazil has developed a tradition of offering sterilisations. A 1991 congressional investigation into the practice estimated that every operation resulted in between seven and 25 votes.

The sterilisation of Indian women is causing even greater concern, however, because their whole civilisation could be jeopardised. Under the Brazilian constitution, Indians are treated like minors and cannot be operated on without the authorisation of a government agency responsible for indigenous groups. Although the Pataxó women apparently gave their consent for the operations, Mr Liebgott said they did not fully understand the implications, believing they were receiving health care.

The Pataxó live in poverty and their children often die of malnutrition. They were told the surgery would reduce the number of offspring. The operations, involving the cutting of fallopian tubes, were carried out on groups - often three to a bed and in unhygienic conditions. Several have suffered complications.

The real issue at stake is land. The Pataxó - who originally occupied 50,000 hectares but are now restricted to 2,000 after invasions by fazendeiros going back to the Fifties - have been fighting for the restoration of their traditional territory. Last year a Pataxó leader was murdered when he took the campaign to Brasilia. A group of youths surrounded Galdino Jesus dos Santos at a bus-stop, poured petrol over him and set him alight.

The government of President Fernando Henrique Cardoso has come under criticism for its handling of the affair. Candidates in next month's poll have been prohibited from entering Indian lands, but calls for Dr Lavigne to be barred from standing in the election have been ignored.

Dr Lavigne is a member of the Right-wing Liberal Front, a party which Mr Cardoso depends on for support. Largely backed by powerful landowners from the north-east, the Front is extremely influential in Congress.

Richard Garside of Survival International, a London-based agency working for the protection of indigenous groups, said: "We are becoming very cynical about the Brazilian government. They say they want to help Indians, but would rather sterilise them than tackle the redistribution of land."