The Labour Party began preparations to nominate him as its candidate from the Dundee Parliamentary constituency in 1939 but that fell through because of his perceived connections with the Communist Party. As Secretary, he built the India League into the most influential Indian lobby in the British Parliament, and actively turned British popular sentiment towards the cause of Indian independence.
Menon became a passionate proponent of India's independence, working as a journalist and as secretary of the India League from 1929 to 1947, and a close friend of fellow Indian nationalist leader and future Prime Minister Jawaharlal Nehru, as well as such political and intellectual figures as Bertrand Russell, J. The origins of what would become the policy of non-alignment were evident in Menon's personal sympathies even in England, where he simultaneously condemned both the British Empire and Nazi Germany, although he did march several times in anti-Nazi demonstrations.
Menon was a passionate opponent of nuclear weapons, and partnered with many in his quest against their proliferation.
During his tenure as the high commissioner, Menon was accused of being involved in the Jeep scandal case of 1948, but the Government closed the case in 1955, ignoring suggestion by the Inquiry Committee.
In 1949, Menon accepted the command of the Indian delegation to the United Nations, a position he would hold until 1962.
He earned a reputation for brilliance in the UN, frequently engineering elegant solutions to complex international political issues, including a peace plan for Korea, a ceasefire in Indo-China, the deadlocked disarmament talks, and the French withdrawal from the UN over Algeria.
Menon's proposal was initially estimated by US diplomats to have more support than the Dulles plan, and was widely viewed as an attempt to hybridise the Dulles plan with Egypt's claims.
Ultimately, the Dulles plan passed, with Menon voting against, alongside Russia, Indonesia and Sri Lanka.