You have a common-law duty of care as an employee. This means that you must exercise reasonable skill and care in your relationship with your employer and colleagues.
In addition, the Health and Safety at Work Act 1974 (HASAWA) requires you to take reasonable care for the health and safety of yourself and other people at work. This extends to co-operating to enable the employer to fulfil its legal duty.
You must not interfere with or obstruct anything provided in the interests of health and safety at work.
An employee who is in breach of his or her duties under HASAWA may be liable to pay a fine on conviction. He or she may also be dismissed from employment for being in breach of a contractual duty to carry out work with proper care and skill – provided the employee was properly instructed about relevant safety measures and had been made aware that the interference could lead to dismissal.