Hold preparatory discussions with elected representatives of British India and the Indian states in order to secure agreement as to the method of framing the constitution.
Set up a constitution body.
Set up an Executive Council with the support of the main Indian parties.
The Mission held talks with the representatives of the Indian National Congress and the All-India Muslim League, the two largest political parties in the Constituent Assembly of India. The two parties planned to determine a power-sharing arrangement between Hindus and Muslims to prevent a communal dispute, and to determine whether British India would be better-off unified or divided. The Congress party under Gandhi-Nehru nexus wanted to obtain a strong central government with more powers compared to state governments. The All India Muslim League under Jinnah, wanted to keep India united but with political safeguards provided to Muslims such as 'guarantee' of 'parity' in the legislatures. This stance of the League was backed up by the wide belief of Muslims that the British Raj was simply going to be turned into a 'Hindu Raj' once the British departed; and since the Muslim League regarded itself as the sole spokesman party of Indian Muslims, it was incumbent up on it to take the matter up with the Crown. After initial dialogue, the Mission proposed its plan over the composition of the new government on 16 May 1946:
Hindu-majority provinces in central and southern India would form another group.
The Central government, stationed in Delhi, would be empowered to handle nationwide affairs, such as defense, currency, and diplomacy, while the rest of powers and responsibility would belong to the provinces, coordinated by groups.
The plan of 16 May 1946 had envisaged a united India in line with Congress and Muslim League aspirations. But that was where the consensus between the two parties ended since Congress abhorred the idea of having groupings of Muslim majority provinces and that of Hindu majority provinces with the intention of 'balancing' each other at the Central Legislature. The Muslim League could not accept any changes to this plan since the same 'balance' or 'parity' that Congress was loath to accept formed the basis of Muslim demands of 'political safeguards' built into post-British Indian laws so as to prevent absolute rule of Hindus over Muslims.
Reaching an impasse, the British proposed a second, alternative plan on 16 June 1946. This plan sought to arrange for India to be divided into Hindu-majority India and a Muslim-majority India that would later be renamed Pakistan, since Congress had vehemently rejected 'parity' at the Centre. A list of princely states of India that would be permitted to accede to either dominion or attain independence was also drawn up.
The Cabinet Mission arrived in India on 23 March 1946 and in Delhi on 2 April 1946. The announcement of the Plan on 16 May 1946 was preceded by the Simla Conference of 1945 in the first week of May.
The approval of the plans determined the composition of the new government. The Congress Working Committee officially did not accept either of the plans. The resolution of the committee dated 24 May 1946 concluded that The Working Committee should consider the connected problems involved in the establishment of a Provisional Government and a Constituent Assembly should be viewed together... In absence of a full picture, the Committee was unable to give a final opinion at this stage.And the resolution of 25 June 1946, in response to the June plan concluded that in the formation of a Provisional or other governance , Congressmen can never give up the national character of Congress, or accept an artificial and unjust parity, or agree to a veto of a communal group. The Committee was unable to accept the proposals for formation of an Interim Government as contained in the statement of June 16. The Committee however, decided that the Congress should join the proposed Constituent Assembly with a view to frame the Constitution of a free, united and democratic India.Jawahar Lal Nehru who later became the first prime minister of India, held a press conference in Bombay declaring that the Indian national congress had agreed only to participate in the Constituent Assembly of India and "regards itself free to change or modify the Cabinet Mission Plan as it thought was the best.
Following consultations, the Viceroy invited 14 men to join the interim government on 15 June 1946. They were Jawaharlal Nehru, Sardar Vallabhabhai Patel, Rajendra Prasad, C. Rajagopalachari and Hari Krishna Mahtab of the Indian National Congress; Mohammed Ali Jinnah, Liaqat Ali Khan, Mohammed Ismail Khan, Khwaja Sir Nazimuddin and Abdul Rab Nisthar of the Muslim League; Sardar Baldev Singh (representing the Sikhs), Sir N.P. Engineer (representing the Parsis), Jagjivan Ram (representing the scheduled castes) and John Mathai (representing the Christians). The Congress proposed Zakir Hussain among its quota of 5 nominees to the interim council. Objecting to this decision, on 29 July 1946, Jinnah announced that his party would not participate in the process to form the Constituent Assembly.
The Viceroy began organizing the transfer of power to a Congress-League coalition. But League president Muhammad Ali Jinnah denounced the hesitant and conditional approval of the Congress and rescinded League approval of both plans. Thus Congress leaders entered the Viceroy's Executive Council or the Interim Government of India. Jawaharlal Nehru became the head, vice president in title, but possessing the executive authority. Vallabhbhai Patel became the Home member, responsible for internal security and government agencies. Congress-led governments were formed in most provinces - including in the NWFP, in Punjab (a coalition with the Shiromani Akali Dal and the Unionist Muslim League). The League led governments in Bengal and Sind. The Constituent Assembly was instructed to begin work to write a new constitution for India.
Jinnah and the League condemned the new government, and vowed to agitate for Pakistan by any means possible. Disorder arose in Punjab and Bengal, including the cities of Delhi, Bombay and Calcutta. On the League-organized Direct Action Day, over 5,000 people were killed across India, and Hindu, Sikh and Muslim mobs began clashing routinely. Viceroy Wavell stalled the Central government's efforts to stop the disorder, and the provinces were instructed to leave this to the governors, who did not undertake any major action. To end the disorder and rising bloodshed, Wavell encouraged Nehru to ask the League to enter the government. While Patel and most Congress leaders were opposed to conceding to a party that was organizing disorder, Nehru conceded in hope of preserving communal peace.
League leaders entered the council under the leadership of Liaquat Ali Khan, the future first Prime Minister of Pakistan who became the finance minister. But the council did not function in harmony - separate meetings were not held by League ministers, and both parties vetoed the major initiatives proposed by the other, highlighting their ideological differences and political antagonism. At the arrival of the new (and proclaimed as the last) viceroy, Lord Mountbatten of Burma in early 1947, Congress leaders expressed the view that the coalition was unworkable. This led to the eventual proposal, and acceptance of the partition of India. The rejection of cabinet mission plan led to a resurgence of confrontational politics beginning with the Muslim League's Direct action day and the subsequent Bihar killings. The portioning of responsibility between the League, the Congress and the British Colonial Administration for this breakdown continues to be a topic of fierce disagreement.