A prominent Catholic cardinal in Hong Kong has embarked on a 72-hour hunger strike protesting against a court ruling that critics say violated Catholics' right to freedom of education.

"I am taking action because last week's ruling has taken away our right to rule schools," 79-year-old Joseph Zen told reporters. "Something precious in Hong Kong has been destroyed."

Last week, Hong Kong's Court of Final Appeal rejected an appeal submitted by the Catholic diocese against a change in the law which in effect forces religious schools to appoint 40 percent of committee members from outside the church.

The government has argued this allows for greater transparency and greater democracy, but critics say it interferes with the schools' management and undermine the freedom of education.

Zen previously said the ruling would turn Catholic schools into non-Catholic ones because the church would no longer have control over their direction.

"Right now, I feel alright, but I don't know about later," Zen said on the second day of his strike, referring to his health.

The 79-year-old, head of the territory's Catholics between 2002 and 2009, has not been afraid to criticise China, even while the Vatican has moved to improve diplomatic ties with Beijing.

On Wednesday the former bishop of Hong Kong admitted he had received HK$20 million from media tycoon Jimmy Lai and said he had used some of the money to help underground religious followers in the mainland, as well as to fund various needy overseas churches.