It shall be the duty of every employer to ensure, so far as is reasonably practicable, the health, safety and welfare of all his employees.

And more specifically, the requirement to:

• Provide and maintain plant and a system of work that is, so far as is reasonably practicable, safe;
  (HSWAct Section 2(2a)

• Provide a suitable and sufficient means of access and a safe place to work;
  (HSWAct Section 2(2d)

• Provide sufficient training, instruction and supervision to employees on the safe system of work;
  (HSWAct Section 2(2c)

Regulation 6. Avoidance of Risks from Work at Height

(1) In identifying the measures required by this regulation, every employer shall take account of a risk assessment under regulation 3 of the Management Regulations.

(2) Every employer shall ensure that work is not carried out at height where it is reasonably practicable to carry out the work safely other than at height.

(3) Where work is carried out at height, every employer shall take suitable and sufficient measures to prevent, so far as is reasonable practicable, any person falling a distance liable to cause personal injury.

(4) The measures required by paragraph (3) shall include-

(a) his ensuring that the work is carried out-

(i) from an existing place of work; or

(ii) (in the case of obtaining access and egress) using an existing means,

which complies with Schedule 1, where it is reasonably practicable to carry it out safely and under appropriate ergonomic conditions; and

(b) where it is not reasonably practicable for the work to be carried out in accordance with sub-paragraph (a), his providing sufficient work equipment for preventing, so far as is reasonably practicable, a fall occurring.

(5) Where the measures taken under paragraph (4) do not eliminate the risk of a fall occurring, every employer shall-

(a) so far as is reasonably practicable, provide sufficient work equipment to minimise-

(i) the distance and consequences; or

(ii) where it is not reasonably practicable to minimise the distance, the consequences of a fall; and

(b) without prejudice to the generality of paragraph (3), provide such additional training and instruction or take other additional suitable and sufficient measures to prevent, so far as is reasonably practicable, any person falling a distance liable to cause personal injury.