"I learnt a lesson. I didn't protect myself enough," he said.

Tai said that at the height of the Occupy movement's sit-in protest at Admiralty he had been overwhelmed by the clashes between protesters and police, meaning that when the computer centre at the University of Hong Kong told him his account had been hacked, it was merely a sideshow among all the drama.

"I was too busy to care. Later I changed my password but still got hacked again. In the end, I needed someone to come down to Admiralty and help me take back a signed form to HKU to change it again."

That move came too late however. The hacked emails were soon sent to the media in batches, exposing Tai's correspondence with other Occupy leaders in which they talked about how to handle donations Tai had received and passed on to HKU, some of which he used for pre-Occupy activities.

Tai insisted he did not breach any HKU rules on donations, but pro-Beijing newspapers accused him of taking money from unknown sources, which led to an internal inquiry at HKU and penalties being imposed on him, including a three-year ban on supervising researchers and receiving donations.

His former boss, Johannes Chan Man-mun, who handled some of the funds, is now under pressure to pull out of the running for a key HKU managerial post.

In a recent article published in , Tai advised other Hongkongers engaged in the battle for democracy to "first protect themselves" against the "gigantic" Communist Party apparatus. He said people should keep their computers secure, make sure there are no illegal structures in their flats, and avoid complicated relationships or financial problems.

But he laughed off suggestions he is overly anxious, saying he speaks from his and other politicians' experience.

"I don't have any fear. I have done nothing wrong," he said. "But you do need to protect yourself before fighting."