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.
Legislation for the Council Tax was introduced and passed in the 1991/1992 session. Also at this time (opponents have said that it was as a cover), the government took the opportunity to review the structure of local government throughout Great Britain.
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 county council of Berkshire, and the creation of unitary authorities covering many of the larger urban districts of England.
The previous system in Scotland had been the regions and districts. These were quite unbalanced in terms of population — the Strathclyde region had nineteen districts and over two million people, whereas the Borders region had four districts and only 100,000 people.
The Act established 29 new 'council areas', and retained the three Island Councils. Variance in population was much less in the council areas, with just over half a million in the largest authority, City of Glasgow, compared to 50,000 in the smallest on the mainland, Clackmannanshire. These are however outliers, and only six are outside the range 75,000 to 250,000.
In some cases the names of traditional counties were revived as administrative areas, although often with vastly different borders.
The 1974 reform in Wales had abandoned use of the names of the historic counties of Wales as local government areas. This was partially reversed in 1996, with Anglesey, Carmarthenshire, Cardiganshire, Denbighshire, Flintshire, Monmouthshire and Pembrokeshire all reappearing as local government areas, although not necessarily with their traditional borders.
The names and areas of the administrative counties abolished in 1996 remained in use (with modifications) as the preserved counties of Wales for purposes such as Lieutenancy.