Must Clause 4 of the framework agreement on fixed-term work contained in the Annex to Directive 1999/70 be interpreted as precluding national legislation which, in respect of the same set of facts (the termination of a contract for services (contrata) between the employer and a third-party undertaking at the latter’s instigation), provides for a lower level of compensation for (i) termination of a fixed-term contract (contrato) for a specific task or service with a term of the same duration as that of the contract between the employer and the third-party undertaking than it does for (ii) termination of the permanent contracts of comparable workers under a collective redundancy that is justified on production-related grounds pertaining to the employer and arises from the termination of the contract between the employer and the third-party undertaking?

If the answer is in the affirmative, is the unequal treatment between workers on fixed-term contracts and comparable permanent workers as regards compensation for termination of contract in cases where termination is prompted by the same factual circumstances but based on different legal grounds to be considered to constitute discrimination of the type prohibited in Article 21 of the Charter, inasmuch as it is contrary to the principles of equal treatment and non-discrimination in Articles 20 and 21 of the Charter, which form part of the general principles of EU law?