1980 housing act.
"Half the proceeds of the sales were paid to the local authorities, but they were restricted to spending the money to reduce their debt until it was cleared, rather than being able to spend it on building more homes. The effect was to reduce the council housing stock, especially in areas where property prices were high such as London and the south-east of England. This trend was exacerbated by a government imposed ban on local authorities using their revenues from council house sales to fund new housing.[8] Both these policies, together with rising rents and cuts to state benefits, have been linked to vast increase in homelessness, when rough sleepers became an increasingly common sight. Homeless households in England during the 1980s, trebled from approximately 55,000 (1980) to 165,000 in 1990.[9]
200,000 council houses were sold to their tenants in 1982, and by 1987, more than 1,000,000 council houses in Britain had been sold to their tenants, although the number of council houses purchased by tenants declined during the 1990s.[10]"