Not in the UK unless you have approval from your flight ops inspector and they have jumped through some hoops to satisfiy the CAA you are operating under multi crew SOP's.
There are currently no approvals in the UK for multi crew ops for SEP-SPA aircraft.
Its a whole load of paper work and changes including another multi crew LPC to be able to log it. I have worked for 2 companys which had such approval and it certainly isn't the case you can stick anyone in the RHS and they can log it or for that matter any airframe will do. There were 2 aircraft which were legal for multi crew and 2 that wern't it was mainly to do with instrument fit.
Its been argued on here before that a safety pilot should be able to log co-pilot when the AP is tits up. But again this is another false statement.
If its a private operation it is impossible to log multi crew time in a SPA.