Minister's Office but were later apprehended and "charged with abetment to overawe the government by force". Operation Coldstore led to the arrests of Nanyang University students who had been involved in opposing the referendum in 1962, and the termination of the Nanyang University student publication permit. These actions triggered widespread student protests against the repressive PSSO. In addition, the student unions of polytechnics, Nanyang University and the University of Malaya jointly produced a proclamation against the arrests and termination of their publication permit. Amnesty International came to the fore and campaigned against Operation Coldstore from its headquarters in London, although their efforts were not successful. Criticisms of treatment of detainees The conditions under which the detainees were held came under scrutiny by the Singapore Assembly when it was revealed that the detainees were kept in "solitary confinement until their interrogation had been completed" while "the interrogation process itself appeared to be unnecessarily protracted." The extended length of interrogations also alarmed the British. In addition, in late May 1963, the British investigating team of Members of Parliament from the Labour Party, which included Fenner Brockway, questioned the manner in which the detainees were treated. 1963 Singapore General Elections and formation of Malaysia The Barisan Sosialis was the People's Action Party's strongest contenders in politics. However, Operation Coldstore had substantially weakened the Barisan as most of its key personnel had been detained. According to Matthew Jones, "the Barisan never recovered from the combined effects of the outcome of the referendum result and the 'Coldstore' detentions.” Jones also highlights that numerous Barisan leaders and members were bogged down with lawsuits and its followers were "demoralised". In addition, Tan Jing Quee mentions that "the two main pillars of the left-wing movement in Singapore, the Barisan Sosialis and SATU, were decapitated," following Operation Coldstore. Operation Coldstore also set off the May Day rally in Farrer Park which was popularly supported by 39 left-wing unions and amassed a crowd of approximately 10,000 people. The rally was accompanied by a call by ST Bani, the president of SATU, who "urged that a general election be held in Singapore under United Nations auspices". In the end, the People's Action Party won the 1963 General Elections and Singapore merged with Malaya, Sarawak and North Borneo to form Malaysia on 16 September 1963. Debates and controversies The extent of communist threat An ongoing debate on Operation Coldstore is whether the