According to the board in T 936/04, "double patenting" is not a ground of opposition. It is, however, within the discretion of the departments of the EPO to raise the objection in opposition or opposition appeal proceedings against proposed amended claims, but this should be done only in clear cases. The purpose behind the principle of the prohibition of double patenting is to avoid unnecessary duplication of effort, and not to impose on the departments of the EPO an obligation to make a complex comparison between the case before them and the claims that may have been granted in some other proceedings. In the case at issue, at the time of the decision by the opposition division, a patent had not yet been granted on the divisional application. For this reason alone the opposition division was correct to disregard the objections of double patenting raised before it. At that stage it would only be a matter for the examining division, in the proceedings on the divisional application before it, to avoid double patenting by again allowing claims already granted in the parent patent.