Ethiopia is denying opposition supporters food, other aid, loans and government services in a widespread effort to suppress political dissent, according to Human Rights Watch.
Much of the aid is provided by foreign governments such as the US and Britain and international financial institutions such as the World Bank, the rights group says in its report, Development Without Freedom: How Aid Underwrites Repression in Ethiopia.
"The Ethiopian government is routinely using access to aid as a weapon to control people and crush dissent," said Rona Peligal, Human Rights Watch's Africa director. "If you don't play the ruling party's game, you get shut out. Yet foreign donors are rewarding this behaviour with ever-larger sums of development aid."
Ethiopian government officials were not immediately available for comment.
According to the group, Ethiopia received $3bn (£1.9bn) in aid in 2008. Donors have privately told Human Rights Watch they are aware of the allegations but they do not know the extent of any abuse. The donors, however, have not conducted an independent assessment into how aid is used in Ethiopia, the group said.
The report says rural villagers reported that many families of opposition members were barred from participation in the food-for-work or "safety net" programme that supports 7 million people.