Winston Churchill spoke of the need to introduce compulsory labour camps for "mental defectives" in the House of Commons in February 1911. In May 1912, a Private Members' Bill entitled the "Feeble-Minded Control Bill" was introduced in the House of Commons… It rejected sterilisation of the "feeble-minded", but had provision for registration and segregation.

The bill was withdrawn, but a government bill introduced on 10 June 1912 replaced it, which would become the Mental Deficiency Act 1913.

At the height of operation of the Mental Deficiency Act, 65,000 people were placed in "colonies" or in other institutional settings. The act remained in effect until it was repealed by the Mental Health Act 1959.

from another article:

The pages of Winston Churchill’s biography is a chapter short. Written by his son Randolph the sibling was too ashamed to go into any detail about the letter his father wrote to British statesman H.H. Asquith.

Behind the parotic speeches of fighting them on the beaches Sir Winston Leonard Spencer-Churchill fought another battle to keep the vulnerable out of sight hidden in the dunes.

In December 1910 the British PM sent a letter to Asquith stating: “The unnatural and increasingly rapid growth of the Feeble-Minded and Insane classes, coupled as it is with a steady restriction among all the thrifty, energetic and superior stocks, constitutes a national and race danger which it is impossible to exaggerate.”

When Churchill moved to the Liberal benches in 1904 he tried to push through tougher legislations for the “feeble minded” after researching a controversial act which was being carried out in Indiana.

The Eugenics Law made it compulsory for criminals and the mentally unfit to be sterilised, they were also not given the right to marry. Reading the act in a book written by Dr. H.C.Sharp Churchill asked the Home Office to put the laws into practice on these shores for the “Feeble-Minded” and research the legal requirements so he could introduce the sterilisation process.

His proposed actions were challenged by Chief Medical Advisor Dr. Horation Donkin who called the laws “The outcome of an arrogation of scientific knowledge by those who had no claim to it….It is a monument of ignorance and hopeless mental confusion.”

Churchill wasn’t one to back down. In 1910 he told the Government Britain’s 120,000 “feeble-minded “people should be “segregated under proper conditions so that their curse died with them and was not transmitted to future generations.” Angered his views on sterilisation had been aborted the leader argued the “feeble-minded” should be segregated from the opposite sex.

Defending his case Churchill said sterilising would come as a much cheaper cost opposed to sending the “feeble minded” to colonies and surgery would allow them “to live freely in the world without causing much inconvenience to others.”