The only opinion that counts is not the one we hear more often but what is clearly written down on the jar-fcl 1.080 "Recording of Flight time".
It clearly states that a copilot may log the time as Picus time when some conditions are met.
(1) Pilot-in-command flight time
(i) The holder of a licence may log as pilot-in-command time all of the flight time during which he is the pilot-in-command.
(ii) The applicant for or the holder of a pilot licence may log as pilot-in-command time all solo flight time and flight time as student pilot-in-command provided that such SPIC time is countersigned by the instructor.
(5) PICUS (Pilot-in-command under supervision)
Provided that the method of supervision is acceptable to the Authority, a co-pilot may log as PIC flight time flown as PICUS, when all of the duties and functions of PIC on that flight were carried out, such that the intervention of the PIC in the interest of safety was not required.
(iii) The holder of an instructor rating may log as pilot-in-command all flight time during which he acts as an instructor in an aeroplane.
(d) Presentation of flight time record
(1) The holder of a licence or a student pilot shall without undue delay present his flight time record for inspection upon request by an authorised representative of the Authority.
(iv) The holder of an examiner’s authorisation may log as pilot-in-command all flight time during which he occupies a pilot’s seat and acts as an examiner in an aeroplane.
(2) A student pilot shall carry his flight time record logbook with him on all solo cross-country flights as evidence of the required instructor authorisations.
(v) A co-pilot acting as pilot-in-command under the supervision of the pilot-in-command on an aeroplane on which more than one pilot is required under the type certification of the aeroplane or as required by JAR–OPS provided such pilot-in-command time under supervision (see (c)(5)) is countersigned by the pilot-in-command.
[Amdt. 1, 01.06.00](vi) If the holder of a licence carries out a number of flights upon the same day returning on each occasion to the same place of departure and the interval between successive flights does not exceed thirty minutes, such series of flights are to be recorded as a single entry.
INTENTIONALLY LEFT BLANK
(2) Co-pilot flight time
The holder of a pilot licence occupying a pilot seat as co-pilot may log all flight time as co-pilot flight time on an aeroplane on which more than one pilot is required under the type certification of the aeroplane, or the regulations under which the flight is conducted.
(5) PICUS (Pilot-in-command under supervision)
Provided that the method of supervision is acceptable to the Authority, a co-pilot may log as PIC flight time flown as PICUS, when all of the duties and functions of PIC on that flight were carried out, such that the intervention of the PIC in the interest of safety was not required.