The structure of local government in the United Kingdom underwent large changes in the 1990s. The system of two-tier local government introduced in the 1970s by the Local Government Act 1972 and the Local Government (Scotland) Act 1973 was abolished in Scotland and Wales on 1 April 1996 and replaced with unitary authorities. In England, some areas remained two-tier but many unitary authorities were created. No changes were made to local government in Northern Ireland.
Prior to the 1970s, the UK had had a mixed system of local government, with some areas being covered by a county council and a more local district council, while large towns had only a single tier of authority (in England and Wales these were termed county boroughs, and in Scotland 'counties of cities'). The Acts abolished the existing county boroughs or counties of cities, and created a uniform two-tier system of government with regions or counties, and districts.
In 1986, Margaret Thatcher's government abolished the county councils of the six metropolitan counties that had been created in 1974, along with the Greater London Council, effectively creating 68 new single-tier authorities: 32 London boroughs and 36 metropolitan boroughs.
In 1990, Thatcher's government introduced the Community Charge, popularly known as the Poll Tax, a new way of funding local councils based on a fixed per-head fee. This proved very unpopular, and led to riots. Eventually, Thatcher was ousted by her own party, and the new Conservative leader and Prime Minister, John Major, was pledged to abolish the Community Charge.