The People's Action Party (PAP) has confidence in its candidate selection process and will stand by its candidates as long as it is satisfied they are fit for the role, Prime Minister Lee Hsien Loong said yesterday.

"If problems come up, we will look at them," PM Lee told reporters when introducing the Ang Mo Kio GRC team that he is leading. "You can never say that nothing is there, and if something turns out to be there, we have to deal with it.

"And if nothing is there, then we back our candidate, and he or she must know that if they've done nothing wrong, if they are straight and open and candid with the party, and we know what is the truth, and we are satisfied that he is fit to be a candidate, we will stand by him and we will defend him."

PM Lee, who is PAP secretary-general, was responding to a question on Mr Ivan Lim, 42, a newcomer who was introduced as a candidate last Wednesday but has since withdrawn his candidacy, following online allegations about his past behaviour.

This question is not just about Mr Lim, but raises a broader point about the quality of the PAP's candidates and the assurance that these are "good people... who want to do good work for Singapore", PM Lee said.

The party, he added, chooses, assesses and vets candidates in a thorough process. But he acknowledged no process or candidate is perfect.

Expressing confidence in those the party is fielding in the July 10 polls, he said: "We are putting together a team of men and women with varied backgrounds and experiences. They've been knocked about, they've learnt about life, they've made mistakes along the way, and hopefully have learnt from them."

He added: "I would say we have a good process, we have got good candidates, and we have got confidence in how the process has worked this time, and in the candidate line-up which we have produced and presented to you this election."

Social media has made it very easy for such criticisms to be circulated and gain currency, whether or not they are well-founded, said the Prime Minister.

In the past few days, online criticism has been levelled at a few other PAP candidates, including Temasek enterprise development director Shawn Huang and former Community Chest managing director Ng Ling Ling. Social media attacks are "not a new thing", pointed out PM Lee, citing the case of incumbent MacPherson MP Tin Pei Ling.

Ms Tin was introduced as a PAP candidate in 2011, to stand in Marine Parade GRC. Then aged 27, she was mocked and criticised when a photograph of her striking a pose with a Kate Spade handbag made the rounds online.

PM Lee noted that she was flamed online and had a very tough time. "For a young woman going into public life to start off like that, it's not an easy matter."

But the party had confidence in her and kept her on, he said. In 2015, she was fielded in single-seat MacPherson, carved out of Marine Parade GRC, and "held her ground amply". "This election, she's standing in MacPherson SMC again, and I don't see lots of people waiting to jump upon her," PM Lee said.

"I think if we look for the perfect candidate, we will lose many good men and women," he added. "And if we encourage a culture of trial by Internet, then we will not find anybody willing to stand and put themselves and their families through this ordeal, even if at the end of it they are able to clear themselves."

On the case involving Mr Lim, PM Lee said Mr Lim did the right thing to withdraw and not let the controversy be a distraction at the polls from more serious issues.

But the party will investigate the veracity of the allegations when the election is over, he added.

"We can't let such serious things be said about somebody and have somebody leave with a cloud permanently hanging over him, and a question mark," PM Lee said. "It would set a very damaging precedent that you can condemn somebody and write him off on the basis of an Internet campaign."

He added: "We don't have time to settle it now, but we can't simply write off and destroy people like this."

Senior Minister Tharman Shanmugaratnam made similar remarks yesterday at a separate event, where he introduced PAP new face Xie Yao Quan, 35, who will replace Mr Lim.

The party takes what has been said about Mr Lim very seriously, but also wanted to be fair to him, he said. "We will find the best way of dealing with it, we take very seriously the issues and we don't want to have a cloud hanging over Ivan unnecessarily, so let's be fair about it."