A high-profile Chinese church leader has been jailed in a week of public confessions and trials of activists deemed opponents of the Chinese state.

Hu Shigen, a leader of a large underground church movement, was previously in prison for 16 years for the charge of counter-revolution after he shared information about the crackdown on protesters in Tiananmen Square in 1989. That charge has since been abolished and he was released in 2008.

But on Tuesday he was sentenced to another seven and a half years for subversion. He pleaded guilty to "damaging national security and harming social stability" according to state media.

It is part of a wider crackdown with several activists sentenced this week. Seen as an attempt to silence opponents, the trials have zero credibility according to human rights activists.

About 300 lawyers and other critics have been arrested since last year in a wholesale round-up. The families of those arrested say they have had no access to their relatives and the Washington-based China Human Rights Defenders say the trials prove China has no commitment to the rule of law.

A number of those arrested, including Hu, have released public confessions which one expert said were the result of brainwashing.

"To say that her statement was 'probably' the product of coercion is silly since she has been held in an immensely coercive environment for over a year,"Jerome Cohen, an expert on Chinese law at New York University, wrote in a blog post on Wednesday.

"These 'confessions' are reminiscent of the 'brainwashing' era of the 1950s for which the new China became infamous."