SINGAPORE - Former political detainee Poh Soo Kai maintains that a 1963 roundup of leftists in a swoop code-named Operation Coldstore was politically motivated, and disputes Law and Home Affairs Minister K. Shanmugam's characterisation that it was mounted on grounds of national security.

His views, set out in a post on the Facebook page of civil society group Function 8 on Sunday (April 15), was in response to Mr Shanmugam's statements about a communist conspiracy in the 1950s and early 1960s when the minister grilled historian Thum Ping Tjin for about six hours during the Select Committee hearings on deliberate online falsehoods.

Dr Poh, who was among more than a hundred leftist politicians and trade unionists arrested for suspected pro-communist and subversive activities in February 1963, said Operation Coldstore must be situated in its particular historical context.

He said the issue was whether Singapore was independent or a British colony at the time of Operation Coldstore.

"If you accept that Singapore was not an independent nation then, in other words that it was a colony controlled by Great Britain. So what do you mean by 'national' in that context?" he wrote.

Singapore had achieved internal self-government in 1959, with the British relinquishing control over everything except defence and foreign affairs. On internal security matters, the British could give inputs through representatives on the Internal Security Council.

Dr Poh, a former assistant secretary-general of the now-defunct Barisan Sosialis opposition party, claimed that the assertions of a "great communist influence" during the period were exaggerated.

He also asserted that the late prime minister Lee Kuan Yew had attempted to mask Operation Coldstore as an operation against the leftists in Peninsula Malaysia, instead of "an operation to lock up his political opponents in Singapore".

"We must learn from history and not myths, history that is grounded in the events and realities of the time," wrote Dr Poh.

The Government has previously rejected Dr Poh's claims that Operation Coldstore was an exercise that targeted Mr Lee's political opponents.

Dr Poh was detained between Feb 2, 1963, and Dec 13, 1972, and re-arrested in 1976 for allegedly plotting to revive Communist United Front activities. On his release in 1982, he practised as a doctor for eight years before moving to Canada. He returned to Singapore in 2007.

He had earlier recounted his personal and political history in a book, Living In a Time Of Deception, which was published in 2016. His post on Sunday was the most recent on the issue of Operation Coldstore.

During the Select Committee hearings in March, Dr Thum cited documents from the Special Branch - the agency that preceded the Internal Security Department - and argued that there was no sustained communist underground conspiracy after the period around 1953 or 1954 because it had been heavily smashed.

However, Mr Shanmugam told Dr Thum that his interpretation of those documents was flawed, and that even if there had not been any instructions for violent action from the Communist Party of Malaya (CPM) leaders, it did not mean there was no communist conspiracy among the lower levels of the organisation.

For example, there may have been specific groups of CPM cadres who were organising actions, such as the Hock Lee bus riots , without instructions from the top.

"The ultimate Marxist-Leninist aim of having a united front organisation that would infiltrate a variety of trade unions, middle schools, political parties on the road to struggle was completely in place," said Mr Shanmugam.

"Operational difficulties meant that on specific occasions there were no instructions given for specific actions. In fact... the cadres took it on themselves to go and do a lot. That doesn't prove there's no conspiracy."

Following questions during the hearing, Dr Thum conceded that there were parts of his Asia Research Institute research paper which he could have worded better.

For instance, while he had said that there was a unanimous call by Barisan Sosialis members to keep following peaceful constitutional action in order to achieve power in Singapore in late 1962, he later acknowledged that armed struggle was also an option that they had kept open at that time.