Former prime minister Dr Mahathir Mohamad has described the late Singapore founding father Lee Kuan Yew as "kiasu" (excessively competitive) over the latter's tough stance in negotiations.

Mahathir said Lee’s relationship with Malaysia was "coloured with bitterness" over Singapore's expulsion from the federation.

As such, Mahathir said it was difficult to deal with Lee when he became prime minister.

"We had 20 problems to resolve and I spent 22 years (as prime minister) trying to resolve them, but I could resolve none.

"He will not give even an inch; kiasu , you know," he told a dialogue with students in Cyberjaya today.

Among the issues, Mahathir said, was how Sabahans and Sarawakians working in Singapore could withdraw funds from the central provident fund but Malaysians from peninsula Malaysia could not.

"They are all Malaysian citizens. We must be treated as one country but there was no progress," he said.

'Which authoritarian ruler resigns?'

Mahathir added that even after Lee retired, he could not push matters with Singapore.

"When we wanted to build a bridge (to Singapore), he (Lee) who had retired came and told me, you have to wait for when Goh Chok Tong (Lee's successor) is not around because he had a nostalgia with the (old) causeway," he said.

Mahathir also denied being an authoritarian leader when he was prime minister from 1981 to 2003, stating that if he was, he would not have relinquished power.

He added that Lee was however a different case. Even though the long-term leader relinquished power, he remained in the government in different capacity.

"Which authoritarian ruler resigns? Can you tell me?

"Lee Kuan Yew resigned as prime minister but he was still in the government as senior minister and minister mentor.

"I left completely and I don't want to come back," he said at a dialogue organised by What Youth Should Know as part of its global leadership series.

Mahathir’s criticism of Lee came less than a week after the grand old man of Singapore politics passed away.

The legacy left behind by the long-term leader - especially his human rights record - was the subject of heated online debate, not only by Singaporeans but also Malaysians.