(90)Contracts should be awarded on the basis of objective criteria that ensure compliance with the principles of transparency, non-discrimination and equal treatment, with a view to ensuring an objective comparison of the relative value of the tenders in order to determine, in conditions of effective competition, which tender is the most economically advantageous tender. It should be set out explicitly that the most economically advantageous tender should be assessed on the basis of the best price-quality ratio, which should always include a price or cost element. It should equally be clarified that such assessment of the most economically advantageous tender could also be carried out on the basis of either price or cost effectiveness only. It is furthermore appropriate to recall that contracting authorities are free to set adequate quality standards by using technical specifications or contract performance conditions. In order to encourage a greater quality orientation of public procurement, Member States should be permitted to prohibit or restrict use of price only or cost only to assess the most economically advantageous tender where they deem this appropriate. To ensure compliance with the principle of equal treatment in the award of contracts, contracting authorities should be obliged to create the necessary transparency to enable all tenderers to be reasonably informed of the criteria and arrangements which will be applied in the contract award decision. Contracting authorities should therefore be obliged to indicate the contract award criteria and the relative weighting given to each of those criteria. Contracting authorities should, however, be permitted to derogate from that obligation to indicate the weighting of the criteria in duly justified cases for which they must be able to give reasons, where the weighting cannot be established in advance, in particular because of the complexity of the contract. In such cases, they should indicate the criteria in decreasing order of importance.