The increasing integration of social and environmental criteria into specifications is driven by both external pressures and internal business motivations. Stakeholder pressure (B) is a primary external driver, encompassing demands from customers, investors, governments (through legislation), and non-governmental organisations for greater corporate responsibility. This forces organisations to embed sustainability into their procurement practices. Concurrently, process efficiencies (A) act as a powerful internal driver. By specifying criteria that reduce waste, energy consumption, or material use, organisations can achieve significant cost savings and operational improvements, creating a strong business case for sustainability that aligns environmental goals with financial performance (the triple bottom line).

C. Insufficient financial resources: This is a constraint or barrier that would hinder the adoption of potentially more expensive sustainable options, not a driving force for their use.

D. Scarcity of environmentally sustainable suppliers: This represents a supply market challenge or a barrier to implementing sustainable procurement, rather than a reason to increase the use of such criteria.

E. Carbon footprint measure: This is a tool or a key performance indicator (KPI) used to quantify and manage environmental impact, rather than a fundamental driving force itself. The drivers are the reasons why an organisation would want to measure its carbon footprint, such as stakeholder pressure or efficiency goals.

1. Chartered Institute of Procurement & Supply (CIPS). (2018). CIPS Level 4 Diploma in Procurement and Supply

L4M3 Commercial Contracting Study Guide. Page 115-116. The guide explicitly lists drivers for ethical and responsible sourcing

including "reducing costs" (which relates to process efficiencies) and "managing reputational risk" and "compliance with legislation" (which are forms of stakeholder pressure).

2. Carter

C. R.

& Rogers

D. S. (2008). A framework of sustainable supply chain management: moving toward new theory. International Journal of Physical Distribution & Logistics Management

38(5)

360-387. https://doi.org/10.1108/09600030810882816. In their foundational model (Figure 1

p. 368)

the authors identify "External pressures/incentives" (e.g.

regulation

customers

society) and the potential for "improved economic performance" as key antecedents or drivers for sustainable supply chain management.

3. Walker

H.

Di Sisto

L.

& McBain

D. (2008). Drivers and barriers to environmental supply chain management practices: Lessons from the public and private sectors. Journal of Purchasing and Supply Management

14(1)

69-85. https://doi.org/10.1016/j.pursup.2008.01.007. The study categorises drivers of environmental supply chain management

prominently featuring "Regulations

" "Customers

" and "Societal pressures" (all forms of stakeholder pressure) alongside internal drivers like "cost reduction" (a direct outcome of process efficiency).