The Singapore Democratic Party (SDP) conducted its first walkabout in Punggol East on Sunday.

Led by secretary-general Chee Soon Juan, a group of 50 members and volunteers visited Rivervale Mall and 20 housing blocks this morning.

Also part of the group were party treasurer Vincent Wijeysingha, and Dr Paul Tambyah, raising speculation that either may be chosen as SDP's candidate in the single-member constituency. Dr Wijeysingha is a lecturer and Dr Tambyah is an infectious disease expert who has spoken at SDP's rallies and worked on several of its policy papers.

Dr Chee won't be eligible to run for an election till 2015.

Even though Prime Minister Lee Hsien Loong has yet to call for a by-election, at least four opposition parties and an independent have indicated their interest in contesting.

Besides the SDP, they are the WP, the Singapore Democratic Alliance, the Reform Party, and former Singapore People's Party member Benjamin Pwee.

RP and SDA have also done walkabouts in Punggol East.

Meanwhile, Dr Wijeysingha declined to comment yesterday on a legal tussle between him and Acting Manpower Minister Tan Chuan-Jin.

Dr Wijeysingha yesterday apologised to Mr Tan for making defamatory comments about him in a Facebook note he wrote on the recent SMRT bus drivers' strike.

He now faces a claim for damages that has yet to be finalised but could amount to tens of thousands of dollars.

Asked yesterday if SDP would help raise money to pay the damages, Dr Chee said it was between Dr Wijeysingha and Mr Tan and would not comment.

But, he added, the turn of events was "very, very disappointing".

"We look forward to a Singapore where politics can be debated, where we can really have reasoned argument instead of legal action being taken," he said.