Sharing specific ConstantContact contacts

We are an independent sales agency that represents manufacturers to wholesale distributors. We are commission-based only from these manufacturers. We have an "Email Plus" account with CC since 2016. We have a manufacturer that we represent requesting the contacts that pertain to them: they want both distributors' and contractors' info. I would think that those contacts are our propietary information, as well as, they would need to have each contact opt-in for 'their' email marketing. Our distributors have told us they do not want us giving their info to their vendor. The manufacturer now wants us to give them the contractors' info, and we do not feel right in doing so. Any thoughts from the community and/or CC?