Who is reponsible for the qualification of project team members?

It sounds like group Managers are sending you their weakest employees to fulfill their obligations to the project while retaining their strongest employees for their own group's work.
If you have no choice but to accept the junior resources you've been sent, then document their lack of experience as a project risk and bring it to your superiors' notice often.

Thank you for bringing up this topic—it’s very relevant to the ground realities we often face. In my experience, project managers rarely have full control over resource selection; resources are usually assigned by functional teams based on availability rather than suitability. This can lead to junior or less-experienced team members being placed in critical roles without proper preparation.

On the ground, this creates a ripple effect. Project managers not only have to focus on delivery but also take on the responsibility of upskilling these resources, which stretches timelines and creates frustration within the team. Superiors may have good intentions of “developing” employees through real-world exposure, but without proper mentorship or training beforehand, the pressure shifts to the project team to compensate for the gaps.

In an ideal scenario, resources should be adequately trained and supported by their originating teams before joining projects. But in reality, it often comes down to the project manager stepping in to ensure results, even if that means additional effort to coach and guide team members. This disconnect between expectations and ground reality is something I believe organizations need to address to ensure sustainable project success.