Siblings Together offers looked-after children the chance to spend the last Saturday of every month with their brothers and sisters at a specialist activity centre in north London.
The service is free to councils, open to all looked-after children and aims to offer an alternative to traditional contact centres.
Social workers are simply required to fill out a referral form to enrol a child onto the scheme, which offers activities such as canoeing, horse riding and ice skating.
Delma Hughes, director of Siblings Together, told CYP Now that she fears the initiative will lose its funding if councils fail to use the service.
"After running this for six months with volunteers we have only just received some small funding, which pays for the centre hire and costs, the activities and some admin," she said.
"Our funders have stepped in to help at this stage, but they will not be able to justify continually sponsoring services that are undersubscribed."
Hughes warned that social workers seem reluctant to refer children because it requires some paperwork.
But she said the charity is willing to help complete the forms if it means children can meet with their brothers and sisters away from the usual "sterile" contact centre environment.
"I can’t see why local authorities wouldn’t want to try this," she said. "We offer a neutral space away from their different carers’ homes, where brothers and sisters can actually continue their relationships with the support they need, which includes all the fun and adventure that all children deserve in their lives."
She added that investing in sibling relationships gives children the security of having family members they can stay in touch with once they leave care.
"I am fully aware that sibling contact is not a duty for local authorities and many people assume these relationships will keep going without any support," she said.
"But the emotional, practical and protective factors that flow from such relationships are vast. What we most want at this point is to reach more social workers and carers to tell them about this service."
