Labour Code section 5 declares:

(1) In connection with employment relations the principle of equal treatment must be strictly observed.

(2) Any consequences of the breach of the principle of equal treatment shall be properly remedied; the remedy shall not result in any violation of or harm to the rights of another worker. 

Labour Code section 142/A declares:

(1) In respect of the remuneration of employees for the same work or for work to which equal value is attributed the principle of equal treatment must be observed (principle of equal pay).
(2) The equal value of work for the purposes of the principle of equal treatment shall be determined based on the nature of work, its quality and quantity, working conditions, vocational training, physical and intellectual efforts, experience and responsibilities.
(3) (3) For the purposes of Subsection (1) 'wage' shall mean any remuneration provided to the employee directly or indirectly in cash or kind, as well as social benefits, based on his/her employment.
(4) The wages of employees - whether based on the nature or category of the work or on performance - shall be determined in compliance with the principle of equal treatment (Section 5).

You can find here the original text of the Labour Code