He was active in politics and served as the chairman of the British Labour Party from 1945 to 1946 and was a professor at the London School of Economics from 1926 to 1950.

[citation needed] In particular, his teaching greatly inspired students, some of whom later became leaders of the newly independent nations in Asia and Africa.

He was perhaps the most prominent intellectual in the Labour Party, especially for those on the far left who shared his trust and hope in Joseph Stalin's Soviet Union;[5] however, he was distrusted by the moderate Labour politicians who were in charge,[citation needed] such as Prime Minister Clement Attlee, and he was never given a major government position or a peerage.

[13] Laski cultivated a large network of American friends centred at Harvard, whose law review he had edited.

His long friendship with Supreme Court Justice Oliver Wendell Holmes Jr. was cemented by weekly letters, which were later published.

[15] Laski returned to England in 1920 and began teaching government at the London School of Economics (LSE).

[16] At the LSE in the 1930s, Laski developed a connection with scholars from the Institute for Social Research, now more commonly known as the Frankfurt School.

[15] Describing Laski's approach, Kingsley Martin wrote in 1968: He was still in his late twenties and looked like a schoolboy.

His lectures on the history of political ideas were brilliant, eloquent, and delivered without a note; he often referred to current controversies, even when the subject was Hobbes's theory of sovereignty.

And it was all immense fun, an exciting game that had meaning, and it was also a sieve of ideas, a gymnastics of the mind carried on with vigour and directed unobtrusively with superb craftsmanship.

He argued that the state should not be considered supreme since people could and should have loyalties to local organisations, clubs, labour unions, and societies.

[21] Laski became a proponent of Marxism and believed in a planned economy based on the public ownership of the means of production.

From the late 1920s, his political beliefs became radicalised, and he believed that it was necessary to go beyond capitalism to "transcend the existing system of sovereign states".

[24] Between the beginning of World War II in 1939 and the attack on Pearl Harbor in 1941, which drew the United States into the war, Laski was a prominent voice advocating American support for the Allies, became a prolific author of articles in the American press, frequently undertook lecture tours in the United States and influenced prominent American friends including Felix Frankfurter, Edward R. Murrow, Max Lerner, and Eric Sevareid.

"[29] Laski's main political role came as a writer and lecturer on every topic of concern to the left at that time, including socialism, capitalism, working conditions, eugenics,[30] women's suffrage, imperialism, decolonisation, disarmament, human rights, worker education, and Zionism.

He felt betrayed by MacDonald in the crisis of 1931 and decided that a peaceful, democratic transition to socialism would be blocked by the violence of the opposition.

[21] During the war, he supported Prime Minister Winston Churchill's coalition government and gave countless speeches to encourage the battle against Nazi Germany.

[33] In 1942, he drafted the Labour Party pamphlet The Old World and the New Society calling for the transformation of Britain into a socialist state by allowing its government to retain wartime economic planning and price controls into the postwar era.

[34] In the 1945 UK general election campaign, Churchill warned that Laski, as the Labour Party chairman, would be the power behind the throne in an Attlee government.

The next day, accounts of Laski's speech appeared, and the Conservatives attacked the Labour Party for its chairman's advocacy of violence.

[37]Columbia University professor Herbert A. Deane identified five distinct phases of Laski's thought that he never integrated.

Newman observes: "It has been widely held that his early books were the most profound and that he subsequently wrote far too much, with polemics displacing serious analysis.

"[21] In an essay published a few years after Laski's death, Professor Alfred Cobban of University College London commented:Among recent political thinkers, it seems to me that one of the very few, perhaps the only one, who followed the traditional pattern, accepted the problems presented by his age, and devoted himself to the attempt to find an answer to them was Harold Laski.

[42] In his memory, the Indian government established The Harold Laski Institute of Political Science in 1954 at Ahmedabad.

At no time did he falter or compromise on the principles he held dear, and a large number of persons drew splendid inspiration from him.

[46] Perón consistently cited Laski as one of his main political inspirations, along with Franklin D. Roosevelt and Christian socialism.

[52] The posthumously published Journals of Ayn Rand, edited by David Harriman, include a detailed description of Rand attending a New York lecture by Laski, as part of gathering material for her novel, following which she changed the physical appearance of the fictional Toohey to fit that of the actual Laski.

[53] George Orwell, in his 1946 essay "Politics and the English Language" cited, as his first example of poor writing, a 53-word sentence with five negatives from Laski's "Essay in Freedom of Expression": "I am not, indeed, sure whether it is not true to say that the Milton who once seemed not unlike a seventeenth-century Shelley had not become, out of an experience ever more bitter in each year, more alien (sic) to the founder of that Jesuit sect which nothing could induce him to tolerate."

67 of the Labour MPs elected in 1945 had been taught by Laski as university students, at Workers' Educational Association classes or on courses for wartime officers.

[54] When Laski died, the Labour MP Ian Mikardo commented: "His mission in life was to translate the religion of the universal brotherhood of man into the language of political economy.