The National University of Singapore (NUS) said yesterday it was "not aware" of a private exchange that allegedly took place between its former research fellow Thum Ping Tjin and a senior staff member.

An Al Jazeera video interview on Singapore politics, shown on Feb 28, had Dr Thum saying he was privately informed by someone senior in NUS that he "would never be able to work in Singapore as an academic... again" after he began publishing and giving lectures about his research.

The research had been critical of founding prime minister Lee Kuan Yew's use of detention without trial. Dr Thum, who had worked at the university's Asia Research Institute from 2012 to 2014, said his research had "proved that (Mr Lee) had lied about his use of detention without trial from the 1960s onwards".

Yesterday, the NUS spokesman declined to comment on the validity of the claims in the Al Jazeera report that Dr Thum had been penalised for his critical research on Mr Lee. She said Dr Thum had resigned from the institute in October 2014.

Yuen Sin