There is a lot of misunderstanding about the laws about lighting at work - especially amongst employers and managers. There is a tendency to look at lighting issues by carrying out levels surveys (often expressed in 'lux' measurements) rather than being influenced by the opinions and comments of those who have to work in the lighting provided. This does not meet with the legal requirements for lighting at work.
Legal requirements on lighting are contained within the Workplace (Health, Safety and Welfare) Regulations 1992 and, specifically for those working with computers etc., in the Health and Safety (Display Screen Equipment) Regulations 1992.
Workplace (Health, Safety and Welfare) Regulations 1992
Regulation 8(1) states that "Every workplace shall have suitable and sufficient lighting."
Health and Safety (Display Screen Equipment) Regulations 1992
Sections on lighting are contained in the Schedule of minimum requirements under regulations 3. It states:
Any room lighting or task lighting provided shall ensure satisfactory lighting conditions and an appropriate contrast between the screen and the background environment, taking into account the type of work and the vision requirements of the operator or user.
So, it is clear from both of these that the key requirement in determining whether lighting levels are adequate is not a light meter, but input from the workers themselves. If they are not content with the light levels, it is likely that the lighting does not meet the legal requirements of the key laws, regardless of whether lighting lux levels are within the design ranges.