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 single-tier authorities. In England, some areas remained two-tier but many single-tier authorities (designated as Unitary Authorities in England) were created. No changes were made to local government in Northern Ireland. Background 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, pledged to abolish the Community Charge. Legislation for the Council Tax was introduced and passed in the 1991/1992 session. Also at this time the government took the opportunity to review the structure of local government throughout Great Britain. England The Local Government Commission for England was established under the Local Government Act 1992, allowing the Secretary of State to order the commission to undertake 'structural reviews' in specified areas, to create unitary authorities in the two-tier shire counties. After much political debate, the commission's proposals resulted in: The abolition of the counties of Avon, Cleveland, Hereford and Worcester and Humberside, created in 1974 The replacement of the county council of Berkshire with six unitary authorities New unitary authorities covering many of the larger urban districts of England. Scotland The previous system in Scotland had been the regions and districts. These were quite unbalanced in terms of population