The People's Action Party (PAP) would still have a strong mandate even if it were to lose its super majority in Parliament, said Workers' Party (WP) chief Pritam Singh.

Speaking to reporters during a walkabout in Punggol West yesterday, Mr Singh pressed on with what has emerged as one of the key themes of his party's campaign: that a strong opposition presence was important, and voters should not worry about it affecting the PAP government's ability to get things done.

"If you have one-third of the seats in opposition hands, the Government has an incredibly strong mandate. You know it can carry out its agenda, it can pass Bills, you only need 50 (per cent) plus one to pass your Bill, so they will be able to do what they wish to do and what they want to do. Except of course when it comes to constitutional changes, that requires a two-thirds majority, and that is why one-third of the seats in opposition hands is important," he said.

Pointing to changes to the elected presidency in 2016, which introduced a system of reserving an election for an ethnic community if five terms have passed without a president from that community, he said that the lack of a two-thirds majority would make the ruling party have to "go out there and explain to people why certain things have to be done and have to be done immediately".

He also said the Government has shown it is more responsive to people's concerns when it loses seats.

The WP has described obtaining one-third of seats in Parliament as a medium-term goal, given that it is contesting only 21 seats in the election. However, Mr Singh also said that the goal will be a difficult one to achieve.

"The journey to get there will of course be a difficult one and we will have to persuade Singaporeans of the importance of a balance in Parliament."

Calls for voters to help build a robust opposition presence in Parliament have been one of the recurring messages from opposition parties during the campaign, with the Progress Singapore Party and Singapore Democratic Party both calling for the PAP to be denied a two-thirds majority on July 10.

Yesterday, Mr Singh also asked the Government to make clear its revenue and expenditure projections for the rest of the decade, so that the public can judge if the proposed goods and services tax (GST) hike is necessary.

The WP had proposed to scrap the planned GST hike, which will increase the tax rate from 7 per cent to 9 per cent some time between 2022 and 2025, and WP East Coast GRC candidate Kenneth Foo had reiterated it during a Lianhe Zaobao dialogue on Thursday night.

Minister for Trade and Industry Chan Chun Sing had asked in response how Singapore would fund its growing expenditure with an ageing population and infrastructure that needs to be renewed.

Asked about this, Mr Singh suggested that the Government should consider other sources of revenue.

He cited how the Government had increased the amount taken from the investment of Singapore's reserves, through the Net Investment Returns Contribution (NIRC) framework.

"I think there is a view out there that it is alleged that WP wants to raid the reserves, but if we look back to 2006, how much of the NIRC did Singapore use? I think it was about $2 billion at that point. Fast forward today, in about 15 years, we're using about $17 billion to $18 billion every year," he said.

He added that with the addition of Temasek into the NIRC framework, the Government had also "reduced the growth slope of the reserves".

"So what happens is as society evolves, you have to look at ways of how you can support your people better and address issues that are very central to them, like cost of living, for example," he said.

Mr Singh spent the morning in Punggol West with his party's new face Tan Chen Chen and party chairman Sylvia Lim.

Ms Tan will stand against PAP candidate and Senior Parliamentary Secretary for Home Affairs and National Development Sun Xueling in the new SMC carved out of the Pasir Ris-Punggol GRC.

In an interview with The Straits Times on Thursday, Ms Tan, speaking mostly in Mandarin, said that she did not see herself as competing with Ms Sun.

"I don't want to be compared to anyone because I am just trying to do my best, to do what I can for the residents here," added the contracts administrator.