Disability Discrimination is unlawful under the Disability Discrimination Act (DDA) where there is:

• Less favourable treatment of a disabled person than a non-disabled person on grounds of their disability (direct discrimination); such treatment cannot be justified.  Thus, treatment is on the ground of disability if a disabled person would not have received it but for his/her disability, though disability does not have to be the only (or even the main) reason for the treatment complained of.  Examples include generalised or stereotypical assumptions about the disability or its effects.
• Less favourable treatment without justification for a reason relating to a person's disability where the treatment is less favourable than the way in which the employer treats or would treat others to whom that reason does not apply.  The discrimination occurs where the reason for it relates to the disability but is not the disability itself, for example where based on absence due to the disability.
• Failure to make reasonable adjustments where, for example, the tasks in the job description or the physical features of the workplace substantially disadvantage a disabled person compared to a non-disabled person.  The disabled person must show that arrangements at work place him or her at a substantial disadvantage compared to a non-disabled person.  The Code of Practice sets out examples of adjustments that may be made, such as making adjustments to premises, allocating some of the disabled person's duties to another person, transferring a person to fill an existing vacancy, altering the disabled person's hours of work, allowing the person to be absent for treatment, the provision of training or mentoring, acquiring or modifying equipment, modifying procedures for testing or assessments, providing supervision or other support or a combination of adjustments.

• Harassment which is where on grounds of disability there is unwanted conduct that violates a person’s dignity or creates an intimidating, hostile, degrading, humiliating or offensive environment; the conduct will be regarded as harassment if, having regard to all the circumstances, including in particular the complainant’s perception, it should reasonably be considered as having that effect;
• Victimisation which is where a worker has been treated less favourably for alleging discrimination, bringing a claim, giving evidence or taking any other action under the DDA.  It also covers the situation where the employer believes or suspects that the victim has done or intends to take such action.
  

Disability is a physical or mental impairment which has a substantial and long-term adverse effect on the person's ability to carry out normal day-to-day activities.  Usually medical evidence will be required to show that a person has a disability.

The DDA protects job applicants, workers and others in relation to: recruitment, employment terms, promotion, training, dismissal and any other detriment.  It applies to all workplaces, no matter the number of employees.

There are some exceptions.  For further information see the disability discrimination section of the Equality and Human Rights Commission website and the Department for Business Enterprise & Regulatory Reform website.