Under Regulation 7 of the Management of Health and Safety at Work Regulations 1999:
Every employer shall, appoint one or more competent persons to assist him in undertaking the measures he needs to take to comply with the requirements imposed upon him under UK Health & Safety legislation.
When seeking competent assistance employers should look to appoint one or more of their employees, with the necessary means, to provide the Health & Safety assistance required.
If there is no relevant competent worker within the organisation or the level of competence is insufficient to assist the employer in complying with Health & Safety Law, then the employer should enlist an external service or person.
The Health and Safety Executive define a competent person as someone who has sufficient training, experience and knowledge and other personnel qualities that will allow them to assist you effectively in your health and safety responsibilities. The level of competence required will depend on the complexity of the situation and the particular help you need.