Pro-democracy veteran Lee Cheuk-yan has called for a boycott of video conferencing services by Zoom after his account was suspended recently, apparently at the request of Beijing.
Zoom said in a statement that it had temporarily closed three accounts, belonging to users in Hong Kong and the United States, and ended meetings linked to the anniversary of the 1989 Tiananmen massacre.
The company said it had taken the steps because the Chinese government demanded it do so.
Lee, the leader of the Alliance in Support of Patriotic Democratic Movements in China, said on Friday that he was one of those locked out.
He said he now wants his annual subscription fee to be refunded, as he urged people to stop using Zoom.
"It's outrageous that although they said they will not block accounts in the future at the request of the Chinese government, what they're going to do is block all Chinese participants if the Chinese government asks them to. So it's the same," Lee said.
"So what we are opposing is political censorship. It's very obvious they are kowtowing to the pressure from China," he told RTHK's Wendy Wong.
Lee said he does not know what is so illegal about people listening to the outside world about June 4, and that whatever Beijing says it doesn't like, Zoom will be happy to censor.
He added that people criticised him for using Zoom in the first place, but he had wanted to reach a mainland audience.
On Thursday, Lee was informed that he will be prosecuted over a June 4 gathering at Victoria Park which took place despite a police ban on a vigil.