This is a big issue in the USA and repeatedly comes up.
The second pilot is referred to as the SIC in a 2 crew aircraft. However you must not log SIC time unless the aircraft you are in specifically requires a two pilot crew. For example... flying right seat on a King AIr and logging SIC time is no good because a King AIr is certified for single pilot operations.
I'm not sure how this applies to your issue however because You are flying under are different country's regulations. In the US you are allowed to count some SIC time toward the ATP requirement but only if it is logged according with the US guidelines I believe.
Weasil