The warning comes from nineteen development agencies, including CAFOD, Christian Aid, Tearfund, World Vision, Oxfam and War Child.
They said that the massacres carried out by the Lord's Resistance Army in remote communities in Sudan, the Central African Republic and the DRC in the last year had been among the worst in the LRA's 20-year campaign of terror.
In a joint report, the agencies warn that more than 1,000 people have been killed or abducted in nearly 200 separate attacks in the DRC, making the Ugandan rebel group the deadliest militia in the country.
The report details a massacre on Christmas Eve in 2008 and a killing spree in north-eastern DRC and southern Sudan in the ensuing weeks in which 865 women, men and children were beaten to death by LRA militants and hundreds more abducted.
It warns that men, women and children continue to face being abducted, mutilated, raped and killed on a daily basis.
The report notes that a previous military offensive against the LRA, Operation Lightning Thunder, failed to capture any senior rebel commanders and only incited the LRA to carry out brutal retaliations across an area 20 times larger than before.
The agencies believe the international community is not doing enough to protect people in the DRC and Southern Sudan from more attacks.
Marcel Stoessel, head of Oxfam in the DRC, said: "It is unbelievable that world leaders continue to tolerate brutal violence against some of the most isolated villages in central Africa and that this has been allowed to continue for more than 20 years.
"This Christmas families in north-eastern Congo will live in fear of yet another massacre, despite the presence of the world's largest peacekeeping mission."
Mark Waddington, head of War Child UK, said the international community must work harder to stop further brutalities at the hands of the LRA and do more to secure the safe release and reintegration of abductees.
He said: "The LRA is mostly comprised of abducted or coerced adults and children who have been forced to commit horrific acts against their community, making it impossible for them to return home.
"Children are forced to kill and rape, and many are used as 'sex slaves'. This must not be allowed to continue."