SINGAPORE - High standards are expected of political leaders, and not going to jail should not be the benchmark of doing a good job, said Prime Minister Lee Hsien Loong on Thursday.

In a riposte to Workers' Party chief Low Thia Khiang over the Aljunied-Hougang-Punggol East Town Council (AHPETC) issue, PM Lee said: "We expect high standards of our political leaders, and the standards must be performed well and do good for the people. By the time you have to be put in jail it's too late."

During a rally speech on Wednesday night, Mr Low had maintained there was no wrongdoing in WP's management of AHPETC.

He argued that the Corrupt Practices Investigation Bureau would have gotten involved otherwise.

Said PM Lee in response: "To say I haven't gone to jail therefore I have done a good job, if that's your standard of doing a good job, that's very sad."

Mr Low had earlier also criticised the People's Action Party for flip-flopping on its policies, including its population projection of 6.9 million.

On the population issue, PM Lee said: "Our positions are clear. We (are) open, we explain, we justify and we win support. And in the end the population, the voters have to decide whether we are doing the right thing or not ."

PM Lee spoke to The Straits Times while campaigning in Ang Mo Kio on Thursday morning with his wife Ho Ching. He had distributed fliers and posed for pictures with commuters at Ang Mo Kio MRT station, before going to the nearby bus interchange.

He is leading a six-member team to contest Ang Mo Kio GRC against the Reform Party at the polls.

Asked for his assessment on the first full day of campaigning on Wednesday, PM Lee said: "The candidates are all working hard on the ground. Ours are and I think the opposition ones are active too.

"We continue to work . It's still early days yet."