Who is the Employer?
If you are considering taking on seconded or contracted labour, a key point to bear in mind is whether you or the business seconding or hiring out the workers is responsible for them. Such responsibilities include employment protection obligations and vicarious liability for employees (where their acts or omissions during the course of employment cause loss or damage to third parties).
For the purpose of determining who is the employer, a key issue is the degree of control which you retain over the way the job is done. If you have such control, it is likely that you will be considered the employer.
Other factors that have been considered important include mutuality of obligation, method of payment, whether the worker has invested in his own future, who provides tools and equipment etc.
In the interest of certainty, the most effective solution is to agree in writing and in advance with the organisation seconding or otherwise introducing the worker to your business as to who will have continuing responsibility for the worker whilst he is engaged in your business.
In most cases you will probably want to ensure that the seconding or introducing company retains those responsibilities.
Health and Safety
For health and safety at work purposes, you will have specific responsibilities and obligations with respect to contract workers as well as your own employees, including risk assessment and management.