CAFOD is warning a deal signed between the government and FARC rebels in November 2016 is being undermined by the killings of community leaders who are crucial to the peace process.
Ulrike Beck, Colombia Programme Officer for the official Catholic aid agency in England and Wales, told Premier: "The peace agreement hasn't really changed much because they're still terrorised, they still have to flee their homes.
"The peace agreement that we celebrate outside Colombia, in Colombia has meant very little change for the people on the ground, actually."
Cafod says the demobilisation of FARC members under November's agreement has created a "power vacuum" and life for some families has actually got worse.
Ulrike Beck explained: "When the FARC left, the territory was left empty, was occupied by paramilitaries, drug traffickers and also by illegal mining, and this has created lots of problems for the people living there."
Community leaders are believed to play a crucial role in helping return the estimated eight million hectares of land illegally seized by rebels to their rightful owners.
Cafod says eight community leaders were killed last week in the region of Uraba alone, and this undermines efforts to ensure seven million people displaced by decades of conflicts can return home.
Ulrike Beck went on to say: "We need to see the peace agreement with the FARC being implemented, and that can only happen with local leaders.
"If local leaders are getting killed, then it will be very difficult for peace to happen in Colombia."
A second round of peace talks involving Colombia's second largest guerrila group, the National Liberation Army (ELN), gets underway in the Ecuadorean capital Quito on Tuesday.
Listen to Premier's Alex Williams speaking to Ulrike Beck: