The 10 million population number was always a planning parameter and not a target for Singapore, said former chief planner Liu Thai Ker.
In an interview with Chinese daily Lianhe Zaobao published yesterday, Mr Liu said sustainable development requires long-term planning.
If Singapore is to continue to preserve the quality of its landscape despite space and resource constraints, he said, it must plan on the basis of a large enough population.
He was responding to claims during the election hustings by the Singapore Democratic Party that the Government plans to increase Singapore's population to 10 million.
At a dialogue with university students last year, Deputy Prime Minister Heng Swee Keat cited Mr Liu, who had said that Singapore should plan for 10 million people for it to remain sustainable in the long term.
Mr Heng had cited Mr Liu in his response to a question on the Government's 2013 Population White Paper, which projected that Singapore's population would reach 6.5 million to 6.9 million by 2030.
However, he had stressed that the number goes beyond how densely populated Singapore would be, and that social space is as important. He also did not say Singapore should plan for 10 million people - nor did he mention the figure.
Mr Heng added that looking at today's situation, the population is likely to be significantly below 6.9 million by 2030.
Mr Liu said he had not paid much attention to the political debate over the issue, and his comments on Singapore's population were "personal opinions". He stressed that the 10 million figure is not a goal but the worst-case scenario.
The 82-year-old is an architect and former chief executive of the Housing Board, as well as the former chief planner of the Urban Redevelopment Authority (URA). He is currently the founding chairman of Morrow Architects and Planners.
During his interview with Zaobao, he reiterated that he had no contact with the Government or political leaders after he left public service in 1992, and the 10 million figure was a planning benchmark and his remarks on the issue were his personal opinion.
The broader objective, he said, was always to preserve the country's beautiful urban environment, including its green spaces and historic monuments. "If you don't make preparations now, when you need more expressways and MRT lines, where will the land come from?"
He pointed out that when he led URA to develop the Concept Plan in 1991, he had thought that the country's population would hit 5.5 million in 100 years - an estimate that came true 70 years ahead of time.
Singapore's current population is 5.7 million.
Mr Liu said he believes the population number cannot be completely controlled, as it is partly a function of rapid economic growth.
As long as the Government is clean and effective and the economy develops well, the number of jobs will increase. "Unless Singaporeans are asking the Government to damage the economy in order not to increase the population."
He acknowledged concerns about an influx of immigrants and whether the country's infrastructure can cope with a large population. But, he pointed out that train services are an administrative and management issue and not related to population numbers.
He urged Singaporeans to not just see the negatives, but also the positive contributions by foreigners.
He said: "In any case, I don't see a 10 million population coming to pass at my age... I am not worried about myself. I am worried about the younger generation."