APEX

Hi

I have written a procedure which creates a new workspace. The owner of the package has been granted apex_administrator_role. This works fine with SQL Developer/Plus.
But when I try to use this procedure from my Apex page I get User requires ADMIN privilege to perform this operation.
I understand that Apex makes a connection with APEX_PUBLIC_USER, and this can be one of the reasons of the error. But I would like to know if there is some solution:
My code is:

      apex_instance_admin.add_workspace (
        p_workspace          => p_name,
        p_primary_schema     => p_name,
        p_additional_schemas => ''); 

  --p_name is passed as a parameter and workspace and primary_schema name are the same

Habib