At the start of 1962, the PAP's White Paper proposals for merger with the Federation were officially endorsed by the Singapore Legislative Assembly. After 13 days of debate that began on 20 November 1961, during which the government's main political opponents, the Barisan Sosialis (BS), had tried their best to defeat the White Paper through what Lee Kuan Yew remembers as “tedious and repetitious” arguments, the Assembly carried the motion by 33 votes to nil for the Heads of Agreement as set out in the White Paper, with the opposition BS members opting to abstain by absenting themselves during the voting. On 30 January 1962 the Legislative Assembly voted 35 ‘ayes’ (PAP, UMNO, SPA), 13 ‘noes’ (BS), three abstentions to support “in principal the plan proposed by the Tunku for the establishment of the Federation of Malaysia comprising the 11 states of Malaya, the states of Singapore and Brunei, and the territories of Sarawak and North Borneo”. By 1962, it had become clear that merger with the Federation would certainly happen, and on the PAP's terms as spelt out in the 1961 White Paper.

The PAP was on strong, defensible grounds in making its arguments for merger. Few could argue with the fact that a Malayan hinterland was critical for Singapore's political and economic survival. With a growing population, limited physical and natural resources and an economy that was stagnating, Singapore simply could not survive as an independent country on its own. Unable to contest the PAP's argument that merger was an absolute economic and political necessity for Singapore, all that the BS could resort to was to question the Tunku's motive for agreeing to merger with Singapore, and to arguing that the terms of the merger as proposed by the PAP were essentially detrimental to the interests of the people of Singapore. The BS argued that the Tunku's scheme was nothing but a neo-colonialist plot, hatched by the British to help the Federation suppress the radical anti-colonialists in Singapore and thus save the increasingly rightwing PAP government. To support its claims, the BS pointed to the various provisions for merger as stipulated by the Heads of Agreement between the Tunku and Lee. The arrangements, particularly on citizenship and Federal legislative representation for Singapore, the BS alleged, were clearly designed to isolate Singapore politically.