1.3 Compliance with applicable law  1.4 Joint tenders  1.5 Subcontracting  1 Directive 2014/24/EU of the European Parliament and of the Council of 26 February 2014 on public procurement and  repealing Directive 2004/18/EC (OJ L 94, 28.3.2014, p. 65).  6  The tender must comply with applicable environmental, social and labour law obligations established by  Union law, national legislation, collective agreements or the international environmental, social and labour  conventions listed in Annex X to Directive 2014/24/EU 1 . A joint tender (such as a consortium) is a situation where a tender is submitted by a group of economic  operators (natural or legal persons). Joint tenders may include subcontractors in addition to the members  of the group. In case of joint tender, all members of the group assume joint and several liability towards ECDC for the  performance of the contract, i.e. both financial and operational liability. Nevertheless, tenderers must  designate one of the economic operators as a single point of contact (the leader) for ECDC for  administrative and financial aspects as well as operational management of the contract.  After the award, ECDC will sign the contract either with all members of the group, or with the leader on  behalf of all members of the group, authorised by the other members via powers of attorney. Any change in the composition of the group during the procurement procedure may lead to the rejection  of the tender. Any change in the composition of the group after the signature of the contract may lead to  the termination of the contract.  Subcontracting is permitted but the contractor will retain full liability towards ECDC for performance of  the contract as a whole.  If subcontracting is envisaged, the tenderer must clearly indicate in the tender which parts of the work will  be subcontracted. If the tenderer relies on the subcontractors to fulfil the selection criteria (see section 3.2 Selection criteria),  these subcontractors must provide a statement declaring their undertaking to collaborate with the  tenderer in case of award, and the resources that they will put at the tenderers disposal for the  performance of the contract.  If the tenderer relies on the capacity of a subcontractor for economic and financial capacity, ECDC may  require the third party to be jointly liable for the performance of the contract.  Tenderers are required to identify all subcontractors whose share of the contract is above 20 % and whose  capacity is necessary to fulfil the selection criteria.  During contract performance, the change of any subcontractor identified in the tender or additional  subcontracting will be subject to prior written approval of ECDC.