The case law described above is, in principle, equally applicable to cases in which new independent claims are filed in response to a ground for opposition.
In T 610/95 the appellant failed to provide a reasoned argument to show that the filing of new independent claim 5 was indeed necessitated by a ground for opposition. The board referred to G 1/84 (OJ 1985, 299), which made it clear that the opposition procedure was not designed to be, and was not to be misused as, an extension of the examination procedure. It would, in the board's opinion, contravene the principles set out in G 1/84 if it was considered admissible to amend the text of a granted patent during opposition proceedings, while maintaining the sole independent claim under opposition, by incorporating an additional new independent claim which as such had no counterpart in the granted patent and, accordingly, was neither the subject of substantive examination in the examination procedure nor open to opposition owing to its non-existence in the granted patent.
In T 223/97 the board confirmed that the addition during opposition proceedings of one or more independent claims while maintaining the main claim in question could not be considered to be a restriction to the main claim in order to meet the ground for opposition raised against it. Thus the mere addition of new claims to the claims as granted was inadmissible because such amendments could not be said to meet a ground for opposition. Even if they otherwise satisfied the dual conditions of Art. 123(2) and (3) EPC. However, the replacement of one independent claim as granted by several, for example two, independent claims each directed to a respective specific embodiment covered by the independent claim as granted was admissible if the replacement was occasioned by grounds for opposition specified in Art. 100 EPC.
Referring to the above decision, the board held in T 181/02 that only in exceptional cases could the replacement of a granted single independent claim by two or more independent claims be occasioned by a ground for opposition, for example in cases where a granted independent claim covered two specific embodiments. Such a situation might also arise if two granted dependent claims (e.g. claims 2 and 3) were linked in parallel to a single independent claim (claim 1). Then the filing of two independent claims (e.g. including the features of claims 1 and 2, and 1 and 3) might be possible (moreover thereby decreasing the number of claims).
However, in the case at issue, the board saw no reason why it should require two independent claims to overcome an objection based on Art. 100 EPC. It was normally sufficient for the patentee to remain with a single independent claim solely by modifying the granted claim once, i.e. by adding one or more features to the granted single independent claim. Adding a second independent claim was in normal cases not needed to avoid revocation of the patent on the basis of the unmodified or modified granted single independent claim, and furthermore did not do anything to help avoid revocation (see also T 610/95).
Citing the above case law, the board in T 263/05 (OJ 2008, 329) added that, when examining the amendments, it did not have to decide whether the ground for opposition would occasion the replacement of a granted single independent claim by two or more independent claims only in "exceptional cases". Rather, it had to be asked in each individual case whether the proposed amendments were an appropriate and necessary response designed to avoid revocation of the patent and could thus be regarded as occasioned by the grounds for opposition.
In T 937/00 the board noted that the filing of multiple independent claims directed to different inventions might unduly complicate and delay the opposition procedure, in particular when this filing was followed by a series of further amendments. An efficient and possibly complete examination of the opposition might for instance become virtually impossible if subsequent amendments were proposed in a piecemeal way rather than addressing all the objections raised by the other party as soon as these objections arose, if they manifestly gave rise to new issues, in particular if they introduced new claims which did not result from any combination of the claims in the granted version, or if they introduced features for which there was no unambiguous support in the application documents as originally filed.
In T 1/05 the board did not regard the introduction of product-by-process claims as an amendment occasioned by a ground of opposition. The submission of such claims demonstrated that these amendments were not directed addressing a ground of opposition but were intended to compensate for the effects of an amendment that had been made to address such a ground, namely deletion of the product claims.