The agreements relate to a 665-mile pipeline running from the Doba oilfields in Chad to the Atlantic terminal at Kribi in Cameroon.

Andrea Shemberg, an Amnesty legal adviser, said: "The ExxonMobil-led consortium that operates the pipeline is effectively sidestepping the rule of law in Chad and in Cameroon. Human rights are not negotiable items that companies and governments are permitted to eliminate by contract." ExxonMobil rejected the accusations, insisting that the company has a record of condemning human rights violations.

Amnesty's 54-page report claims the agreements could require Chad and Cameroon to give precedence to the interests of the oil companies over the rights of those living near the pipeline or oilfields. Both governments could face financial penalties if they interrupt the workings of the oilfields or pipelines.

Amnesty expressed concern that the ambiguity of such legal contracts - known as host country agreements - create dangerous precedents.

Amnesty said the operation of the oilfields and the pipeline have already led to alleged abuses in which poor farmers in the Doba region have been displaced and refused compensation, while other villagers have been denied access to the only safe water supply. The report adds that Chad and Cameroon have a poor human rights record.

Chad has agreed with the consortium that, within a pipeline's perimeter, it is forbidden for "any person to undertake activities which may interfere with the construction, operation and maintenance" of the pipeline. Cameroon has agreed to a similar clause. Amnesty recommends that the agreements be amended to ensure that human rights take priority over the interests of the consortium.

An ExxonMobil spokesman in the UK yesterday expressed regret that Amnesty had not consulted the company during the preparation of the report.

"ExxonMobil condemns human rights violations in any form and has actively expressed these views to governments and others around the world," the spokesman said.

The spokesman added that in Chad some oil revenues would be used to help social development projects.

An Amnesty spokeswoman, Sarah Green, said the organisation had discussed the report with Andre Madec, an ExxonMobil representative in the public affairs department at its headquarters in Houston, Texas. She said Amnesty was not adopting an aggressive stance but wanted to enter into a dialogue with ExxonMobil and other companies about such agreements.