From a modest 150 words to the length of a children's book - the number of words used by politicians in their election manifestos has grown substantially in the past century, new research shows.
Far from becoming irrelevant because few voters now manage to plough through the mammoth documents, manifestos now have a quasi-constitutional significance, according to historians.
Although manifestos have no formal status in law, they now have a symbolic value as embodying the will of the people, used if necessary to overcome any objections from civil servants or the House of Lords, according to the University of Exeter study.
Professor Richard Toye and Professor David Thackeray have calculated that between 1900 and 1997 the Conservative party used 197,898 words in total in their manifestos, Liberal or Liberal Democrat 127,803 and Labour 142,526.
In 1900 the Conservative manifesto was 880 words long, the Liberal manifesto 1,790 and Labour 150 words. The size gradually grew, and by 1970 the Conservative manifesto was 10,676 words long, Liberal 2,871 and Labour 11,735. By 1997 the Conservative manifesto was 21,053 words long, Liberal Democrat 14,007 and Labour 17,657.
The main part of the 2019 Labour manifesto is 26,175 words long, while the Liberal Democrat manifesto has 28,146 words.
Between 1900 and 1997 manifestos were longest in 1992, with all three parties using a total of 53,259 words, compared to 1910, when parties used just 1,076 words in total in their manifestos.
The analysis, published in the journal Twentieth Century British History, shows all three parties have struggled to be comprehensive, but also ensure their manifesto acts as punchy propaganda. In 1983, Labour's internal crisis meant that it was "unable to prepare a short, popular and lively manifesto" and instead fell back on a previously prepared 22,000 word 'Campaign Document', famously described as being "the longest suicide note in history". Yet politicians could produce shorter manifestos if they wanted, as shown by some of the manifestos of the 1950s, and by Labour's successful efforts in 1987 and 1992 to avoid another overlong document.
Professor Thackeray said: "After 1945 central party staff increasingly dominated election campaigns. Most candidates waited until the party manifesto had been released before finalising their own election address, this meant they were less likely to issue pledges which might clash with the national programme. This meant by the end of the century MPs were chiefly considered representatives of a party with a formal mandate to carry out manifesto pledges."
Labour has used detailed pledges in its manifestos from the 1920s onwards to challenge antisocialist scaremongering and present itself as a credible party of government. After 1950 the Conservative Party used the same tactic, of making their manifestos more specific, to win over cynical voters.
Margaret Thatcher sought to tap into public disillusionment with state intervention, organising Conservative election manifestos around a few, detailed pledges. The later New Labour approach drew on Thatcher's practice, in order to forestall the classic Conservative claim that the party's plans were unaffordable. The Conservatives were the first party to use civil servants to 'cost' an opposition manifesto in 1964.
Professor Toye said: "Although few voters read manifestos from cover to cover, they are still important symbolic part of the electoral process. But in view of their ballooning length many people will ask themselves if politicians, having abandoned the search for the magic money tree, have instead located a magic typewriter."