 Three months after the elections , an armed insurgency by communist groups in Malaya – the Malayan Emergency – broke out . The British imposed tough measures to control left @-@ wing groups in both Singapore and Malaya and introduced the controversial Internal Security Act , which allowed indefinite detention without trial for persons suspected of being " threats to security " . Since the left @-@ wing groups were the strongest critics of the colonial system , progress on self @-@ government was stalled for several years . 
