After gaining independence from Britain, Singapore joined the federation of Malaysia in 1963. Although the PAP was the ruling party in the state of Singapore, the PAP functioned as an opposition party at the federal level in the larger Malaysian political landscape. At that time and until the 2018 general election, the federal government in Kuala Lumpur was controlled by a coalition led by the United Malays National Organisation (UMNO). However, the prospect that the PAP might rule Malaysia agitated UMNO. The PAP's decision to contest federal parliamentary seats outside Singapore and the UMNO decision to contest seats within Singapore breached an unspoken agreement to respect each other's spheres of influence and aggravated PAP–UMNO relations. The clash of personalities between PAP leader Lee Kuan Yew and Malaysian Prime Minister Tunku Abdul Rahman resulted in a crisis and led to Rahman forcing Singapore to leave Malaysia on 9 August 1965. Upon independence, the nascent People's Action Party of Malaya, which had been registered in Malaysia on 10 March 1964, had its registration cancelled on 9 September 1965, just a month after Singapore's exit. Those with the now non-existent party applied to register People's Action Party, Malaya which was again rejected by the Malaysian government, before settling with the Democratic Action Party (DAP).
After gaining independence from Britain Singapore joined the federation of Malaysia in 1963 Although the PAP was the ruling party in the state of Singapore the PAP functioned as an opposition party at the federal level in the larger Malaysian political landscape At that time and until the 2018 general election the federal government in Kuala Lumpur was controlled by a coalition led by the United Malays National Organisation (UMNO) However the prospect that the PAP might rule Malaysia agitated UMNO The PAP's decision to contest federal parliamentary seats outside Singapore and the UMNO decision to contest seats within Singapore breached an unspoken agreement to respect each other's spheres of influence and aggravated PAP–UMNO relations The clash of personalities between PAP leader Lee Kuan Yew and Malaysian Prime Minister Tunku Abdul Rahman resulted in a crisis and led to Rahman forcing Singapore to leave Malaysia on 9 August 1965 Upon independence the nascent People's Action Party of Malaya which had been registered in Malaysia on 10 March 1964 had its registration cancelled on 9 September 1965 just a month after Singapore's exit Those with the now non-existent party applied to register People's Action Party Malaya which was again rejected by the Malaysian government before settling with the Democratic Action Party (DAP)