Singapore Democratic Party (SDP) candidate Paul Tambyah last night said he disagreed with his rival, Dr Vivian Balakrishnan, over what he called a "philosophical point" on ministerial salaries.

Dr Balakrishnan had accused Professor Tambyah yesterday morning of "distorting" his warning - that eliminating allowances for elected Members of Parliament will draw corrupt candidates - into one that is a criticism of the work put in by volunteers for free.

He said that Prof Tambyah had taken his remarks out of context, saying that he was referring to politicians and not volunteers when he spoke at a forum last week.

The two men ran into each other on a morning walkabout at Adam Road Food Centre, and had apparently discussed the matter.

Prof Tambyah, speaking at his party's rally in Jurong East Stadium last night, said he "appreciated the clarification" by Dr Balakrishnan, but stuck to the point that elected MPs who serve the people should not be paid high allowances.

"His view of honesty in politicians seems to be extremely limited to the negative idea of not lying, not cheating, or not giving or receiving favours," Prof Tambyah said.

This was after reading out in full and "in the spirit of gentlemanly debate", a lengthy Facebook post by Dr Balakrishnan on the issue. He added that he believes "honesty in a politician means having a honest view of yourself, knowing that you are primarily a servant of the people, not a master of the people".

"You are not entitled to some extraordinarily high salary just because you are a scholar who doesn't take bribes," said Prof Tambyah.

"Honesty means realising that you are in your job because the people trusted you to speak up for them, and you owe your job to them."

The debate over ministerial salaries erupted after Prof Tambyah said at a rally last Saturday that he did not see the logic of volunteers working for free when MPs are paid high allowances - when both are working to serve the people.

He also said: "Singapore has many wonderful volunteers who help out in many social services... They are not wealthy and certainly not corrupt."

Prof Tambyah, 50, a professor at the Yong Loo Lin School of Medicine, is facing off against a People's Action Party (PAP) team led by Dr Balakrishnan, who is Minister for Environment and Water Resources, in Holland-Bukit Timah GRC.

Also in the SDP team contesting the constituency are party chief Chee Soon Juan, 53; auditor Sidek Mallek, 55; and healthcare administrator Chong Wai Fung, 45.

Dr Chee, who took the stage last, reiterated a point he made on Saturday - that the ruling PAP is not all bad. But he piled the pressure on Dr Balakrishnan, zeroing in on how he had got it wrong in estimating the budget for the Youth Olympic Games (YOG) in 2010, when he was Minister for Community Development, Youth and Sports.

The initial YOG budget of $104 million ballooned to $387 million - three times the original sum - and Dr Balakrishnan had attributed this to his ministry's lack of experience in organising a sports extravaganza on such an Olympian scale.

He had told Parliament then that the overspending was because it was the first YOG, and "both the International Olympic Committee and us were starting from scratch".

Dr Chee cited this incident yesterday when giving his view on the Central Provident Fund (CPF) system, reiterating the party's call for Singaporeans to be given the choice to have their retirement savings returned to them.

"You have absolutely no moral authority to tell Singaporeans that they will squander their savings when you outspend the YOG budget by $300 million."

• Additional reporting by Olivia Ho