Prime Minister Lee Hsien Loong has urged Singapore's ruling party to "reinvent" itself after two landmark elections showed a sharp drop in support following more than half a century in power.

Lee's comments -- published in the People's Action Party's (PAP) magazine Petir and prominently reported in the pro-government Straits Times on Friday -- were in reaction to the May general elections (GE).

The PAP, in power since 1959, won 81 of 87 seats in the May polls but garnered its lowest ever vote share of 60 percent.

Only a controversial system of electing most members of parliament in group constituencies prevented the loss of further seats to the opposition, which had more modest campaign resources and chose to focus on a few districts.

The party's troubles were also highlighted in the August 27 presidential election when former deputy prime minister Tony Tan won with just 35 percent of the 2.1 million ballots cast in a four-cornered race, edging his closest rival by a mere 7,269 votes.

"The PAP must reflect on the meaning of the GE," Lee stated.

"We have to strengthen and reinvent ourselves to maintain our leading role in Singapore politics, so that we can continue to make lasting contributions to our country," he added.

In his message to party members, Lee did not mention the presidential election -- a non-partisan contest for a largely ceremonial job -- but analysts saw the August results as further proof of the PAP's waning popularity.

"The Party needs to improve our engagement and outreach, and involve Singaporeans much more in issues affecting them," Lee said of the May vote.

"The election campaign and results show that Singaporeans also want our politics to evolve, to become more consultative and inclusive. Singaporeans want to be engaged in shaping our future, and want the government to be more responsive to their immediate concerns."

The PAP has been criticised for failing to engage citizens enough in carrying out major decisions such as opening up the city-state to massive casinos and liberalising immigration policy.

The prime minister -- the son of Singapore's founding father Lee Kuan Yew -- emphasised the need to win support from the younger generation by engaging them at the community level as well as through social media.

"We must earn their trust by respecting their views, supporting them in their quest to realise their hopes and dreams, and inspiring them with an exciting vision for Singapore’s future."

"The Party must learn to work effectively in a more fluid political environment," he said.

At its peak, the PAP garnered 86.7 percent of the vote in the 1968 parliamentary polls.

It has gained international admiration for turning Singapore into a developed economy during its rule but has also been widely criticised for cracking down on dissent.