I am employed as a H&S advisor in a busy engineering company. My boss has asked me to visit the site of a potential customer to carry out PUWER risk assessments on a couple of their machines (he is effectively hiring out my services). Before agreeing to take this on, can anyone offer some advice as to where this would place me in terms of responsibility?

I possess the appropriate quals and experience to have no issue with carrying out these risk assessments effectively as it is something I do regularly within our own working environment. However, if I go ahead and risk assess these machines for another organisation would I be putting myself in a position of responsibility towards their risk? Should an accident subsequently occur in their workplace with the equipment concerned, would my document (and therefore me!) be the focus point for scrutiny? Additionally, should any shortcomings be highlighted within that document, could I be held liable for this?

Any help/advice would be gratefully received before I agree to carry out these assessments.

Your employer carries employer liability insurance by law (I'm assuming you are in UK), i.e. covering any act or omission by his/her employees. As you've been instructed to do this work as part of your employment, any resulting liability falls to your employer, not yourself. Only issue would be if your did something reckless, or totally contrary to your instructions, which your employer could argue it was not possible to foresee.

You've already said you are confident the work is within your current competence, so I can't see any problem. Obviously it would be different if you were doing this outside the terms of your employment. That's why IOSH requires all those on its Consultants Register to have their own professional liability insurance.

talk to your insurers as they may not offer cover in this area

You are neither working for the workshop or consulting as such, I dont see harm in carrying out risk assessment for their machines with participation of their staff including operators and supervisors, ie as suggested facilitate a risk assessment session.
Good luck.
Al

To answer your question "could I be held liable for this" I think that the answer is yes, because you are the person carrying out the work, in effect you are a consultant to the client. There have been cases where consultants have been held liable for carrying out risk assessments where shortcomings may have or had lead to an accident or ill health. In my opinion once a person has signed a risk assessment (or any document for that matter) then that makes them accountable for that document, and not nessary the employer. If you have no issues with carrying out these assessments and you do have the relivant quals and experience then you probbly have nothing to worry about.
Remember also that your client has a duty to ensure that the advice that they are sourcing is from competent people.