Prime Minister Lee Hsien Loong yesterday brought Dr Chee Soon Juan's character and ability into focus as issues that voters in Bukit Batok should be concerned about.

The Singapore Democratic Party (SDP) chief had not come clean and was not remorseful about his past, and his character had not changed, said Mr Lee.

"Here is somebody that's (up for election) who is able to just gloss over bad things which have been done, and which he has not come to terms with or acknowledged. And he's now presenting himself as a new man - reinvented - and yet, unchanged, and unregretful and unrepentant," he said.

He made these remarks after a morning walkabout in the constituency with People's Action Party (PAP) candidate Murali Pillai.

Mr Lee said Dr Chee is not what he makes himself out to be.

"What he says is one thing, but the reality is quite different, and what he did yesterday at the rally, allowing his colleagues to hit at David Ong in a most unbecoming manner," he said, having watched the livestream of Friday night's rallies.

"And then he comes along in a benign, almost beatific way, and says 'We must not hit people who are down, that's very bad, anyone can make mistakes - even good people'. I think it shows that his character has not changed."

Mr Lee, the PAP secretary-general, was referring to the SDP's rally, where several speakers from the party took aim at former PAP MP David Ong, who stepped down on March 12 over an alleged affair.

Dr Chee, who was the last to speak at the rally, told the crowd that it was not right to beat a man while he was down.

This was "completely hypocritical", said Mr Lee yesterday.

"You get your guys to say all the bad things, and you come along and you look magisterial and benign and you say, 'You must not hit somebody', having caused all your lieutenants to hit him as hard as they can," he said. "But unfortunately, it's in character."

Mr Lee, who said he would be concerned if Dr Chee was elected into Parliament, added that an interview published in Chinese evening daily Lianhe Wanbao on Friday showed that "he's not sorry for anything he did".

"If you are a changed person, then there must be a basis on which you say: 'What I did previously, I regret, I'm sorry. I now resolve to go in a different direction, I resolve to be a different sort of leader'," he said. "But here he told Wanbao: 'I don't regret anything which I did, all my crazy history. I'm proud of what I had done, and I am what I am'."

Mr Lee also raised questions about Dr Chee's ability to be an MP and manage a town council.

Addressing Dr Chee's pledge to become a full-time MP if he is elected, he said it was easy for Dr Chee, who does not hold a full-time job, to say so.

"It's easy to say, but what do you bring, which you would be able to contribute and show that you can do for the voters? It's partly your record, it's partly your ability, but it's also your character."

This was in contrast to Mr Murali, whose "commitment is beyond doubt", he said. Mr Murali would also be backed by a PAP-run town council which has a good track record.

"The key thing is who has the character, who has the track record, who can you trust. And the PAP town councils will manage it to the best of our ability. We have our reputation at stake," he said.

"I don't say we never make mistakes. But when we do make mistakes, we put them right, and I think overall our track record of managing town councils is good."

Residents are happy with the work of MPs and town councils to improve the neighbourhood, Mr Lee added, citing facilities, like an amphitheatre and multi-purpose hall, that have been built since his last visit to the estate in 2009.

"The residents talked to me about wanting some more benches, they want some extra facilities - these are things which we can do," he said. "But for somebody who comes along with no record, no basis, but says 'I will do a better job' - talk is easy, performance is what counts."

Yesterday, Mr Murali also spoke to reporters to refute Dr Chee's accusation that he would be constrained by the party Whip while debating issues in Parliament.

"For me, being in politics is not an occupation, it's a cause. So why should I muzzle myself? It does not make any sense at all. I will say, I will push, whatever that is necessary to serve the legitimate interests of Bukit Batok residents, or for that matter, Singaporeans," he said.

Mr Lee and Mr Murali spent almost 21/2 hours covering a 1.1km stretch from the Bukit Batok MRT station to a coffee shop at Block 154.

The Prime Minister shook hands, took selfies with residents and told several grandparents he met that he, too, wished to be a grandfather soon.

He also praised Mr Murali's election posters, which feature him with residents - instead of the usual formal portrait of candidates - and remarked that they "really break the mould".

Besides Mr Lee, Mr Murali was accompanied by Jurong GRC MPs, including Deputy Prime Minister Tharman Shanmugaratnam, during his walkabout.

•Additional reporting by Ng Keng Gene