There is no legal requirement that the first claim should be the broadest. However, Art. 6 requires that the claims must be clear not only individually but also as a whole. Therefore, where there are a large number of claims, they should be arranged with the broadest claim first. If the broadest of a large number of claims is a long way down, so that it could easily be overlooked, the applicant should be required either to re-arrange the claims in a more logical way or to direct attention to the broadest claim in the introductory part or in the summary of the description.
Furthermore, if the broadest claim is not the first one, the later broader claim must also be an independent claim. Consequently, where these independent claims are of the same category, an objection may also arise under Rule 6 if they result in a lack of clarity and conciseness (see GL/PCT-EPO F‑IV, 3.2).