The character of an election candidate is important and something voters should be concerned with, Singapore Democratic Party (SDP) chief Chee Soon Juan said.

But voters can see this for themselves, he added, saying: "Character is what people see in you, not what you tell people you have or you don't have."

It also has to be demonstrated and earned, not just talked about, Dr Chee said yesterday, following a weekend where the issue of character has dominated exchanges between the SDP and the People's Action Party (PAP). "If you want to talk about character, then show yourself to have character," he said. "When there is character, you don't have to go and tell other people 'that guy has poor character'. Ironically, it reflects on that person."

He was speaking to reporters after a cycling outreach event in Bukit Batok, where he faces PAP's Mr Murali Pillai in the May 7 by-election.

Dr Chee's remarks come after Finance Minister Heng Swee Keat, a member of the PAP's central executive committee, hit out at the SDP's argument that the character of election candidates should be off limits. Mr Heng said on Sunday that SDP's argument that a person is not defined by his actions or words - made by SDP central executive committee member Paul Tambyah - was "one of the most astounding statements ever made in the history of Singapore politics".

Mr Heng's comments came a day after Prime Minister Lee Hsien Loong, PAP's secretary-general, raised questions about the character of Dr Chee.

PAP did not hold a rally on Sunday but SDP did, and Dr Chee had at his rally called on the ruling party to "stop the gutter politics" and focus on policy issues.

Yesterday, he added there was no need to "run down" a person or talk bad about him. "Character is when you show other people what you can do for them, not how badly you talk about them," he said.

"I keep saying, let's not get into this thing where you show everybody how holy you are, how unblemished you are. People see this in you, (so) be humble."

He also reiterated his view that there is "absolutely no way" an MP can hold a full-time job and still discharge his responsibilities fully.

"The more I come out and talk to people and meet people, the more that you find that it's so ridiculous for MPs to be part-time," he said. "Absolutely no way that you can do the job on a part-time basis."

Dr Chee said he intends to focus on three areas for the rest of the campaign, which will end on Thursday. Cooling-off Day is on Friday, and Bukit Batok residents will vote on Saturday.

Besides pledging to be a full-time MP if he wins, Dr Chee said the SDP will make sure that it takes good care of the town council, while ensuring that it executes its social programmes at the municipal level.

"At the parliamentary level, we've been laying out - and we'll continue to lay out - some of the national issues that we're very concerned about: cost of living and retrenchment insurance," he said.

SDP will also be talking about education, he added. The party will hold a rally tonight.