Singapore's opposition parties do not see it as their duty to solve the nation's problems and plan for the future, said Prime Minister Lee Hsien Loong.
Instead, their main campaigning platform is to act as a "check" on the ruling party, he said at a People's Action Party (PAP) rally held after the party's biennial conference yesterday.
But for every "checker" in Parliament, there will be one fewer "doer, thinker and leader" in the government, said Mr Lee, who is the PAP's secretary-general.
"You will have a lot of checkers, you have no workers... There will be gridlock, like in other countries," he said.
"Eventually, there will be no PAP to check... That will be the last check, because it will be checkmate for Singapore."
In a speech that pulled no punches in criticising the opposition, Mr Lee said that every time the PAP Government puts out a popular policy, opposition politicians respond: "Do more."
But they fail to suggest where the money will come from, or "who are you going to 'take from' in order to 'give more' ", he said.
Mr Lee also chided opposition politicians for not putting forth a vision for Singapore, saying it is "because they are trying to avoid answering hard questions".
The PAP, on the other hand, delivers on its promises and thinks long term, he added. Citing the $8 billion Pioneer Generation Package, which was funded from the surpluses of a single term of government rather than future taxes, he said the ruling party will not "mortgage your children's future to win your votes".
Taking a jab at the 2011 election slogan of the Workers' Party (WP) - the biggest opposition party in Parliament - Mr Lee said: "When other people say First World Parliament, we don't know what it means." He added to loud cheers: "But when we say First World Nation - here we are."
Yesterday, Mr Lee also urged PAP activists to greater action in the lead-up to the next general election (GE), especially in opposition-held wards.
The WP currently controls Aljunied GRC, Hougang and Punggol East - the biggest opposition haul since independence.
Mr Lee said that in June, he visited several thousand Aljunied residents, who gave him a rousing welcome. Pledging to win the opposition constituencies back, he said: "It may take some time, but we will not give up trying and, one day, we will succeed."
He pointed to the example of PAP MP Sitoh Yih Pin, who wrested Potong Pasir back from the opposition on his third try.
Madam Normah Ahmad, 62, a Kaki Bukit activist, agreed: "We should try to win back Aljunied, slowly, if we have to. It is a hard fight, but I think we can."
Activists must also toughen up for the next GE, Mr Lee said.
"For democracy really, truly to work in Singapore, the PAP also must fight, and fight to win the battle," he said. "Because if we sit down and we are good guys and nice and friendly to everybody, I think we deserve to lose."