Someone has already registered that SSH key.

Hi,
I have a work and personal accounts for which I prefer to use one public key for all my SSH access. I have registered a new username and tried to import my public key I use for work account (different username) and got an error "Someone has already registered that SSH key.". Is there a way around this because I won't be using the service if I need a different private/public for every username I work under.

Thanks
Boris