People's Action Party (PAP) MPs must expect sharper questioning and more robust debates in Parliament with more opposition MPs and a Leader of the Opposition in the House, said Prime Minister Lee Hsien Loong.

In an eight-page letter to all ruling party MPs on how they should conduct themselves, released to the media yesterday, PM Lee told them to be prepared to engage the opposition, to clarify their interventions and scrutinise their ideas.

"PAP MPs should express their views frankly, whether for or against government policies. During debates, speak freely and with conviction. Press your points vigorously, and do not shy away from robust exchange," he said in the letter titled "rules of prudence", which is traditionally issued to PAP MPs after each general election.

"However, please exercise judgment when putting your points across, and do not get carried away playing to the gallery," he added.

The PAP won 83 out of 93 seats and 61.2 per cent of the votes in the July 10 polls, in which all seats were contested. With the Workers' Party taking 10 seats, party chief Pritam Singh will formally be appointed Leader of the Opposition.

On the PAP's results, PM Lee said: "The people have endorsed what we have done in our previous term, and given us a clear mandate to take Singapore forward, through the crisis and beyond.

"Now we must work with Singaporeans to keep Covid-19 in check, protect jobs and livelihoods, and make sure everyone comes through safely together."

This time around, PM Lee also specifically addressed the use of social media by MPs in his letter.

He noted that social media has become a part of daily lives and MPs are free to use it to let the public know about their work or their views. He urged them to "have some fun" and to "try out different platforms", but to also be mindful that they are elected public figures.

"So observe decorum, ensure factual accuracy as this is an absolute requirement for us, and remember every social media post will be permanently associated with you and the party," he said. "Be honest, empathetic, positive and affirming in all your messages. Know your audience and be sensitive to how they feel. Do not use social media to attack another person," he added.

PM Lee also reminded MPs that social media is but one way to connect with people, and they have to attend to residents' needs and interact with them in person.

The rest of the letter set out in detail the standards that PAP MPs must abide by in areas ranging from parliamentary attendance to the acceptance of company directorships to receiving gifts.

As in years past, PM Lee stressed the importance of upholding the party's reputation for clean and incorruptible government.

To this end, MPs should separate their public political status from their private business or professional interests, he said. This means they should, among other things, be careful of the invitations and gifts they accept, and ensure they do not lobby public officers on behalf of friends, clients or their employers.

MPs also should not solicit directorships, nor accept those where the company wants to "dress up the board with a PAP MP or two, in order to make the company look respectable".

PM Lee also cautioned MPs against using Parliament to lobby the Government on behalf of their business or clients. "You may, however, relay feedback and speak freely to Cabinet ministers... ministers will listen carefully to arguments on principles, especially when they relate to the general policy of their ministries. But ministers will not exercise their discretion to change individual decisions without very good reasons which they can justify publicly," he said.

Even when raising funds for non-political purposes for constituency and grassroots organisations, MPs have to be extra scrupulous in accepting donations.

He advised them to gather multiple small contributions, rather than depend on one or two large donors so as to "avoid incurring obligations which may expose you to awkward requests later".

PM Lee also urged MPs to always listen closely to Singaporeans, help them tackle pressing needs, and accurately reflect their worries and aspirations to the Government.

"Never break faith with the people," he said.

In Parliament, MPs' honest, informed views are important political input to ministers in policymaking, he told them. And ministers will accept all valid, constructive suggestions, but will also have to challenge inaccurate or mistaken views.

"Over time, the public will see that PAP backbenchers are as effective as opposition MPs, if not better, at holding ministers to account, getting issues fully debated, and influencing policies for the better," he said.

He added that he has asked the Speaker of Parliament to give all MPs, particularly new MPs, ample opportunity and latitude to speak, noting that their first opportunity will be during the debate on the President's Address at the opening of Parliament later this month.

Summing up the letter in a Facebook post sharing it yesterday, PM Lee said: "Whether or not we are in a pandemic, our responsibility as MPs is clear. We are servants of the people, and will carry out our duties with integrity, honesty and incorruptibility. We will always be sensitive to the views and attitudes of the people we represent, and conduct ourselves with humility, modesty, decorum and dignity."