How to make a container trust the certs in the host ca-certificate store

We are having problems getting docker containers to trust the certs in the local ca-certificates store on the host. We are using native docker swarm and have created services and tried mount /etc/ssl/certs on the service to the host equivalant directory with no success.

I’ve not been able to find any one discussing certs except with regards to private repos and UPC.

Has anyone else had any previous experience of doing this successfully?