He is noted for his middle-of-the-road strategy of "simultaneously negotiating with and confronting" Beijing and joined the Beijing-installed Provisional Legislative Council in 1996 despite the pro-democrats' boycott.

He entered the University of Hong Kong in 1974 but was ousted a year after because he spent too much time organising social movements and failed his exams.

He went to the United Kingdom in 1979 and obtained his undergraduate Bachelor of Arts degree in Social Policy and Public Administration at the University of Bradford in 1982.

A moderate pan-democrat, he is known for his middle-of-the-road strategy of "simultaneously negotiating with and confronting" Beijing, which, in his words, is to try to keep contact with the mainland authorities so you will have a chance to convince them to listen to your views.

In the 2015 District Council election, he lost his long held seat in Lai Kok to a 25-year old newcomer, Chan Wing-yan, of the pro-Beijing Hong Kong Federation of Trade Unions (FTU) and Democratic Alliance for the Betterment and Progress of Hong Kong with 99-vote margin, while former ADPL member Eric Wong Chung-ki stood in the constituency, taking away 215 votes.

His decision caused criticism as he was blamed for snatching votes from other pro-democrat candidates including Lee Cheuk-yan which led to his downfall in his long time base.

He participated in the pro-democracy primary of the March 2018 Kowloon West by-election after incumbent Yau Wai-ching of Youngspiration was ousted from the Legislative Council over the oath-taking controversy.

Former vice-chairwoman Rosanda Mok and all ADPL's Yau Tsim Mong and Kowloon City District Councillors quit the party in the midst of the intra-party primary, in protest against Fung's candidacy.

"[5] In October 2018, Fung announced that he was standing in the November Kowloon West by-election, three months after quitting the ADPL, which intended to back unity pro-democracy candidate Lau Siu-lai.

Amid criticism from allies, he declared that he was unhappy that another veteran, Lee Cheuk-yan, was chosen by the pro-democracy camp as Lau's backup, rather than himself, in case she was barred from running.