61According to settled case-law, in all proceedings in which penalties, especially fines or penalty payments, may be imposed, observance of the rights of the defence is a fundamental principle of EU law which must be fully complied with by the Commission (see, to that effect, judgment of 5 March 2015, Commission and Others v Versalis and Others, C‑93/13 P and C‑123/13 P, EU:C:2015:150, paragraph 94 and the case-law cited).