Campaign group Human Rights Watch is urging the UN to immediately stop supporting a military campaign in DR Congo against Rwandan rebels, BBC reported.
It says the UN should wait until it can ensure that joint operations in eastern Democratic Republic of Congo do not violate international humanitarian law.
In a new report the charity charges the UN's continued backing undermines its mandate to protect civilians.
The UN says that overall the campaign is bolstering stability in the region.
The US-based group released its report ahead of UN Security Council deliberations this week on renewing the mandate of UN peacekeepers in the Democratic Republic of Congo.
There has been mounting criticism of the UN's supporting role in a military campaign against Rwandan rebels that has led to the killing of hundreds of civilians.
The Congolese military campaign against Rwandan rebels has led to the brutal killing of hundreds of civilians, and the raping of thousands, including by the very soldiers the UN is supporting.
The Human Rights Watch report says this raises serious concern about whether the peacekeeping mission is implicated in these abuses.
In the new report it urges the UN to end support for the campaign until the adoption of clear and measurable conditions ensuring that joint operations don't violate international humanitarian law.
According to leaked memos cited by the report, UN lawyers had warned about the legal risk of supporting a campaign by an army with such a poor human rights record.
For their part, UN officials argue that the situation for civilians would be even worse if the peacekeepers weren't there.
They have also withdrawn support for one army unit accused of atrocities, and vow to do the same with others if evidence emerges.
When the Security Council considers the renewal of the peacekeeping mandate this week, it is expected to strengthen the focus on civilian protection, however, it is unlikely to end support for the military operations.