The DEC is a coalition of major humanitarian aid charities that work together to respond to major disasters around the world, collectively raising money to help ensure that emergency relief reaches the people who need it most.
The charity works in more than 40 countries, providing emergency responses to those who have been affected by conflict and disaster.
Existing members include Oxfam GB, Christian Aid, Islamic Relief and Save the Children UK.
Melanie Ward, chief executive of the IRC, said the move would put the charity in a stronger position to respond to future crises.
“This comes at a critical time when the devastating combination of conflict, economic turmoil caused by Covid-19 and climate change is seeing an increase in humanitarian needs globally, and a record number of displaced people," she said.
“We are looking forward to working together on protecting and rebuilding lives through effective humanitarian response.
“Coming together with the incredible organisations that are members of DEC will make our shared humanitarian efforts stronger and our impact greater.”
Sue Inglish, chair of the DEC, said: “IRC UK will enhance our collective expertise in responding to refugee and displacement crises, and their work supporting people affected by conflict will be a great asset to the DEC.
“IRC works in many of the toughest and most fragile places in the world and will help DEC appeals reach even more people in need, while also helping mobilise the generosity of the British public and raise funds in response to the world’s worst humanitarian disasters.”
Income at the DEC more than tripled last year after more than £30m was given to its coronavirus appeal.