Double entries in address book

I've got two sets of entries for every contact in my address book on my Mac Mini.

If I click on the groups icon, I can see that there is one group of contacts described as On My Mac and another group described as in the Icloud.

At the moment, if I want to edit or delete a contact, I have to do it twice. Is there any way I can consolidate these two groups? I did try unticking Contacts in System Preferences but that just meant that any changes to my contacts I made in the Icloud were not automatically updated to my Mac Mini, so that's not a solution.

What I need to do is merge the two together, so that I have just one set but so I don't lose any contacts - I've already discovered that there are some unique contacts on each list.


roger

PS I've got the same contacts on my Macbook Air and I don't have the same problem there - there's just one set.