Spreading fear and being populist are not the way to advance democracy in Singapore, said Deputy Prime Minister Tharman Shanmugaratnam on the last night of rallies for the Bukit Batok by-election.

"I am not against a healthy opposition," said Mr Tharman, the last speaker of the rally for People's Action Party (PAP) candidate Murali Pillai.

But he warned against "the politics of spreading fear and alarm and the politics of populism", which he said the Singapore Democratic Party (SDP) has been engaging in. "That's the wrong type of politics for Singapore."

He gave examples like SDP candidate Chee Soon Juan's quoting an article by a Peking University don that said $800 billion is missing from the national reserves. "Absolute rubbish," said Mr Tharman, who noted that the article had been debunked on the Finance Ministry's website.

Similarly, for Dr Chee's claim that only 100 jobs were created last year: "Crazy," said Mr Tharman, adding that anyone with a sense of reality knows that is not so.

The Employment and Employability Institute and Singapore Workforce Development Agency alone created 17,000 jobs, and the Economic Development Board brought in investments that created about 20,000 jobs last year.

"Either you don't know, in which case do the homework, or you know and you're wilfully spreading fear and alarm. Bad! Bad politics."

Dr Chee has pledged to speak up for the elderly until government spending is raised, but Mr Tharman pointed to what has been done in recent years alone, such as the Pioneer Generation Package and Community Health Assist Scheme.

"Spending on the elderly is the largest increase in the government budget than any other item including defence," added the former finance minister.

The Government gave each citizen retiree household about $4,000 in benefits per retiree last year, after taxes. This is twice as much as 10 years ago, after adjusting for inflation. Even the better-off in five- room or executive flats received $2,000 last year in benefits, after taxes - four times what they got a decade ago, after adjusting for inflation.

Mr Tharman also decried populism - "promising the good things without saying how much it's going to cost".

For instance, the SDP does not tell people how much its healthcare proposals will cost, he said. It praises the health system in France, but does not reveal that the ordinary citizen pays 20 per cent of his or her income in taxes just for healthcare.

Also rebutting the SDP on issues of policy was Minister in the Prime Minister's Office Chan Chun Sing, who is also the labour chief. He objected to Dr Chee's "feast or famine" approach to defence spending, saying: "That's not the way we build defence capabilities."

After the arrest of eight radicalised Bangladeshi workers, "suddenly the cry is we must strengthen the immigration controls... But don't forget, not so long ago, we were told to cut the security budget by 30, 40 per cent", said Mr Chan, referring to the SDP's earlier positions.

Summing up his party's campaign, Mr Tharman said Singapore must never end up where the United States is today - once it had a strong consensus in the middle, but it now faces a fragmented population, low social trust and demagogues holding sway, he added.

"Never pursue the politics of division. Always pursue the politics of developing consensus.

"You don't need to agree with the PAP but discuss things openly, tell people the truth. These are the benefits, these are the costs, let's argue what's best. That is how we advance democracy. And it's the track I hope the SDP gets onto," he said.

The Bukit Batok by-election is about who residents can trust, he added. Mr Murali can be trusted to serve: "Not because you're part of his political journey. He will serve you because it's you."

Describing the May 7 polls as a "very tight fight", Mr Tharman said he would congratulate Dr Chee if he wins and wish him well.

But if he loses, Mr Tharman said he would advise him to reflect. Noting that it is the fifth constituency Dr Chee is contesting, he said: "If he loses, please reflect on things. Don't keep blaming the system. And try to change."