In 1908, now considered to be the United Kingdom's leading authority on unemployment insurance, he joined the Board of Trade, and helped organize the implementation of the national system of labour exchanges.
In 1909 Beveridge was appointed Director of Labour Exchanges; his ideas influenced David Lloyd George and led to the passing of the 1911 National Insurance Act. During Asquith's Liberal government of 1908 to 1914 Beveridge was asked to advise Lloyd George on Old Age Pensions and National Insurance; the government began to take action to combat poverty.
In 1919 he left the civil service to become director of the London School of Economics and Political Science (LSE). Over the next few years he served on several commissions and committees on social policy.
Lord Beveridge was so highly influenced by the Fabian Society socialists – in particular by Beatrice Potter Webb, with whom he worked on the 1909 Poor Laws report – that he could readily be considered one of their number. However, he was perhaps the best economist among them – his early work on unemployment (1909) and his massive historical study of prices and wages (1939) being clear testaments to his scholarship. The Fabians made him a director of the LSE in 1919, a post he retained until 1937. His continual jousts with Cannan and Robbins, who were trying to wrench the LSE away from its Fabian roots, are now legendary.
An important role he performed in 1933, which is sometimes forgotten nowadays, was helping set up the Academic Assistance Council. This helped prominent German Jewish academics escape Nazi persecution.
In 1937, Beveridge was appointed Master of University College, Oxford.
The Report to the Parliament on Social Insurance and Allied Services was published in 1942. It proposed that all people of working age should pay a weekly national insurance contribution. In return, benefits would be paid to people who were sick, unemployed, retired or widowed. Beveridge argued that this system would provide a minimum standard of living "below which no one should be allowed to fall".
It recommended that the government should find ways of fighting the five 'Giant Evils' of Want, Disease, Ignorance, Squalor and Idleness. This led to the setting up of the modern Welfare State (the culmination of the Fabians' project) with a National Health Service (NHS):
19.Plan for social security : XI.Medical treatment covering all requirements will be provided for all citizens by a National Health Service organised under the health departments and post-medical rehabilitation treatment will be provided for all persons capable of profiting by it.
One of its most remarkable assets was the convincing manner of Beveridge's argument which made it so widely acceptable: Beveridge appealed to conservatives and other doubters by arguing that the welfare institutions he proposed would increase the competitiveness of British industry in the post-war period, not only by shifting labour costs like healthcare and pensions out of corporate ledgers and onto the public account, but also by producing healthier, wealthier and thus more motivated and productive workers who would also serve as a great source of demand for British goods.
Beveridge saw full employment (which he defined as unemployment of no more than 3%) as the pivot of the social welfare programme he expressed in the 1942 Beveridge Report, and Full Employment in a Free Society (1944) expressed how this goal might be gained. Alternative measures for achieving it included Keynesian-style fiscal regulation, direct control of manpower, and state control of the means of production. The impetus behind Beveridge's thinking was social justice, and the creation of an ideal new society after the war. He believed that the discovery of objective socio-economic laws could solve the problems of society.
The following year the new Labour Government began the process of implementing Beveridge's proposals that provided the basis of the modern Welfare State. Clement Attlee and the Labour Party defeated Winston Churchill's Conservative Party in the 1945 general election. Attlee announced he would introduce the Welfare State outlined in the 1942 Beveridge Report. This included the establishment of a National Health Service in 1948 with taxpayer funded medical treatment for all. A national system of benefits was also introduced to provide 'social security' so that the population would be protected from the 'cradle to the grave'. The new system was partly built on the National Insurance scheme set up by Lloyd George in 1911.
In 1946 Beveridge was made Baron Beveridge, of Tuggal in the County of Northumberland, and eventually became leader of the Liberals in the House of Lords. William Beveridge was the author of Power and Influence (1953). He died at his home on 16 March 1963 and was buried in Thockrington churchyard, on the Northumbrian moors. His barony became extinct upon his death.
His last words, as he sat up in bed whilst still working on his 'History of Prices', were "I have a thousand things to do".