The Three-Day Week was one of several measures introduced in the United Kingdom by the Conservative Government 1970–1974 to conserve electricity, the generation of which was severely limited due to industrial action by coal miners. The effect was that from 1 January until 7 March 1974 commercial users of electricity were limited to three specified consecutive days' consumption each week and prohibited from working longer hours on those days. Services deemed essential (e.g. hospitals, supermarkets and newspaper prints) were exempt. Television companies were required to cease broadcasting at 10.30 pm during the crisis to conserve electricity. 
Throughout the mid 1970s, especially 1974 and 1975, the British economy was troubled by high rates of inflation. To tackle this, the government capped public sector pay rises and publicly promoted a clear capped level to the private sector. This caused unrest among trade unions as wages did not keep pace with price increases. This extended to most industries including coal mining, which provided the majority of the country's fuel and had a powerful trade union.
By the middle of 1973, the National Union of Mineworkers (NUM) - drawn from a workforce who almost wholly worked for the National Coal Board - were requiring their members to work to rule; and as imports were economically unattractive, coal stocks slowly dwindled. The global effect of the 1973 oil crisis also drove up the price of coal. The administration of Prime Minister Edward Heath entered into negotiations with the NUM, to no avail. To reduce electricity consumption, and thus conserve coal stocks, Heath announced a number of measures on 13 December 1973, including the "Three-Day Work Order", more commonly known as the Three-Day Week, which came into force at midnight on 31 December. Commercial consumption of electricity would be limited to three consecutive days each week. Heath's objectives were business continuity and survival and to avoid further inflation and a currency crisis. Rather than risk a total shutdown, working time was reduced to prolong the life of available fuel stocks. This was designed to be short-term remedial austerity that reduced wages for people, a sort of economic rationing as seen until 1954 but of a different product: coal.
In an act of brinkmanship, Heath called the February 1974 general election while the three-day week was in force. His government emphasised the pay dispute with the miners and used the slogan "Who governs Britain?". The election resulted in the Conservative Party losing its majority, (although without consequence having the largest share of the vote), while Labour became the party with the most seats (had a plurality) in the House of Commons, without an overall majority (a Hung Parliament). In the resulting talks, Heath failed to secure enough parliamentary support from the Liberal and Ulster Unionist MPs; and Harold Wilson returned to power in a minority government. The normal working week was restored on 8 March, but other restrictions on the use of electricity remained in force. A second general election was held in October 1974 cementing the Labour administration, which gained a majority of three seats.
In the campaign for the 1979 General Election, after the Winter of Discontent running into that year, both main adversaries had startling graphic advertisements: Labour reminded voters of the Three-Day Week, with a poster showing a lit candle and bearing the slogan "Remember the last time the Tories said they had all the answers?" and they ran with Callaghan on his arrival back from a conference in Guadeloupe who played down the crisis. The Conservatives took advantage of this in saying "Crisis, What Crisis?". The Conservatives' message prevailed, and Margaret Thatcher became prime minister. Their main campaign slogan was "Labour Isn't Working".
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