5. c. 28) was an act of Parliament of the United Kingdom creating provisions for the institutional treatment of people deemed to be "feeble-minded" and "moral defectives".

[6] The Commission returned a lengthy report in 1908 which estimated that of a population of 32,527,843 British inhabitants 149,628 people (0.46%) were considered "mentally defective".

It recommended the establishment of a board of control which would oversee local authority efforts aimed at "the well-being of the mentally defective".

[9] One of them was Josiah Wedgwood, who attempted to filibuster and said of it, "It is a spirit of the Horrible Eugenic Society which is setting out to breed up the working class as though they were cattle.

[14] In 1916, reasons for people being referred to the London County Council's Mental Deficiency Committee included being unable to keep a job, epilepsy, having had illiegitimate children, homelessness, and living in an "unsatisfactory" (i.e., impoverished) home.

[15] People categorised under this Act would often be sent to a new kind of institution called a "mental deficiency colony" rather than an insane asylum or a prison.