SINGAPORE - Prime Minister Lee Hsien Loong criticised Dr Chee Soon Juan on Saturday, labelling the Singapore Democratic Party chief "hypocritical" and "unrepentant".
He noted the SDP rally on Friday during which several speakers from the opposition party took aim at former People's Action Party (PAP) MP David Ong, who stepped down on March 12 over an alleged affair.
Yet Dr Chee, who was last to speak at the rally, told the crowd that it was not right to beat a man while he was down.
Mr Lee, who is the PAP secretary-general, told reporters after a walkabout in Bukit Batok constituency on Saturday that this was "completely hypocritical".
"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."
He also said he was "saddened but not surprised" to read Dr Chee's interview on Friday with the Lianhe Wanbao Chinese evening daily "because he's not sorry for anything he did".
"He (said he) is proud of his record, he is proud of his crazy history, and yet when he comes today, he presents himself as a changed man."
Mr Lee noted that Dr Chee had talked at Friday's rally about the need to give everyone a second chance , but said that Dr Chee has not acknowledged his own mistakes.
He questioned Dr Chee's claims of being a changed man.
"He says last night (Friday) at the rally, even good people make mistakes, you must give them a second chance. But before you can turn around and make good, you must first recognise that something has gone wrong, and that you have to put it right. Which in this case, if there's nothing that has gone wrong, there's nothing to put right - then how can we have changed?"
Mr Lee recalled a speech that he himself made during last year's general election in which he spoke about Dr Chee "and said that he's (Dr Chee) absolutely right, that character never changes, and that of all people , he should know that best".
He also noted that some comments left on Dr Chee's Facebook page pertaining to race have not been refuted or taken down.
The PAP candidate for the May 7 by-election, Mr Murali Pillai, is Indian.
"So I have no doubt that somewhere along the way, when pressures heat up, people will feel that, maybe, this is one way you can use race to your advantage. I think it's wrong," Mr Lee said.
But Mr Murali has proven himself in Paya Lebar ward in Aljunied GRC, which he contested at last September's general election, he said.
"Mr Murali has shown in Paya Lebar, that even despite his being Indian and not Chinese, he is able to connect, he's able to serve voters, he's able to win their confidence and win their votes," he said.
He added: "If Paya Lebar was a single-member constituency, Murali would be the MP right now."
Mr Lee also said that voting for Mr Murali would mean the estate will be run by an experienced town council.
"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," he said of Dr Chee's promises.
As for Dr Chee's pledge that he would serve as a full-time MP, Mr Lee noted that the SDP chief has not been working full-time: "Now he says I'm going to work full-time for you. It's easy to say. But what do you bring which you would be able to contribute and show that you can do for voters? And it's partly your record. It's partly your ability, but it's also your character."