As a young minister in the 1980s, Mr Lee Hsien Loong had helped then Deputy Prime Minister Goh Chok Tong and his team develop the elected presidency scheme, which started out as a concept by founding Prime Minister Lee Kuan Yew.

He later assisted then Law Minister S. Jayakumar in drafting the White Papers on the scheme, published in 1988 and 1990.

As Prime Minister, he has also worked closely with two elected presidents, Mr S R Nathan and Dr Tony Tan Keng Yam, and had sought and received approval from Mr Nathan to draw on the reserves during the 2008 global financial crisis.

Yesterday, Mr Lee pointed to his familiarity with the elected presidency scheme as he explained why the institution needed to be adjusted now.

"I am doing it now because it would be irresponsible of me to kick this can down the road and leave the problem to my successors.

"They have not had this long experience with the system, and will find it much harder to deal with," he said.

His experiences, he said, have given him insight into what the intention of the elected presidency scheme was when it was formulated, how it has worked in practice, how conditions have changed, and how the system should be fine-tuned.

"Since the elected presidency began, I have been operating the mechanism that we designed, and discovering its glitches.

"I helped to refine and amend the scheme as we went along," he said during the debate on the proposed changes to the elected presidency under the Constitution of the Republic of Singapore (Amendment) Bill.

While the institution has been functioning well, he added, the changes made now are in the long-term interests of Singapore and will strengthen the elected presidency, which is an important stabiliser in the political system.

But further changes will still be needed in the future as the system has to be continually refined, he said.

"I am sure the result will not be perfect. I fully expect that one day, my successors will find it necessary to make further improvements and adjustments to the elected presidency scheme."

Mr Lee added that the refinements are "not cast-iron and foolproof", and things can still go wrong with politics in Singapore.

What the changes will do is reduce the chances of this, he said, adding: "Ultimately our safety, and our future, lie in the hands of Singaporeans. We must rely on Singaporeans to remain united, so that our politics can be constructive and cohesive."