But Mr Guerindon said he could have done both jobs because he was not required to be physically present in Paris.
The Fos also claimed it was entitled to revise Mr Guerindon's job description under the terms of his contract.
One of the differences between the work of adjudicators in general casework and those in mass claims is that the former do not act as the first point of contact for members of the public.
The tasks of taking telephone calls from the public and setting up new cases on the system are known as "pre-conversion" tasks and these tasks are carried out by adjudicators in mass claims.
Incoming calls from the public are handled on a shift system and each adjudicator is assigned a one-hour shift every day.
The reorganisation - and the creation of the role of investigator - was intended to create a role which did not specialise in a particular area and to make the Fos more responsive to complaints by moving towards a more telephone-based role, solving problems immediately where possible.
The Fos has been approached for comment.
damian.fantato@ft.com
