86It follows from the above that the principal characteristic of contracts of employment as contract staff for auxiliary tasks is their insecurity over time, in line with the very purpose of such contracts, which is to arrange for occasional staff to perform duties which — by their nature or by virtue of the absence of a holder of the post — are insecure. That regime may not therefore be used by the AECE to assign tasks corresponding to a ‘permanent post’, as defined in paragraph 77 above, tasks corresponding to a post included in the list of posts annexed to the section of the budget relating to each institution, which the budgetary authorities have defined as temporary (see paragraph 81 above), or manual or administrative support service tasks, within the meaning of Article 3a(a) of the CEOS, for long periods to such staff, who would thus be used outside the proper framework at the cost of prolonged uncertainty (see, to that effect and by analogy, Deshormes v Commission, paragraph 80 above, paragraphs 37 and 38, and Case 43/84Maag v Commission [1985] ECR 2581, paragraphs 18 and 19). After all, such a use would infringe the principle prohibiting abuse of rights as applied to the use by the AECE of successive fixed-term employment contracts in the public service (paragraphs 71 et seq. above). It would also be contrary to the principle of equal treatment in the public service (Case C-227/04 PLindorfer v Council [2007] ECR I-6767, paragraph 63, and Case C-71/07 PCampoli v Commission [2008] ECR I-5887, paragraph 50), according to which staff who are objectively placed in identical conditions or situations must be subject to the same rules.