Hong Kong's largest teachers' union announced it would disband on Tuesday following a growing number of attacks from pro-Beijing newspapers, among dozens of civil society groups to do so since the ruling Chinese Communist Party (CCP) imposed a draconian national security law on the city from July 1, 2020.

The Professional Teachers' Union (HKPTU) said it would begin the process of dissolving with immediate effect, in a statement on its official website.

"After much deliberation and thorough investigation ... the Executive Committee unanimously resolved to dissolve HKPTU," union president Fung Wai-wah said in a letter to members.

"The HKPTU's 48-year history has reached the last chapter, and the last full-stop," the letter said. "This is a tragic and deplorable situation, certainly, but looking back over our long years of struggle and development, we should have no regrets."

"We sincerely plead for your understanding and acceptance of what was a no-choice, unwanted and difficult decision," Fung wrote.

"It is deplorable that radical changes to to our sociopolitical environment have left us wondering about our futures," the letter said.

The union said it would lay off 200 staff and sell off its assets, beginning immediately.

State media attack

Founded in 1973 by former teacher and lawmaker Szeto Wah, the union began protecting teachers' rights and providing services for them out of a tiny office in Yau Ma Tei, Kowloon.

The move came after the PTU was described by CCP mouthpiece the People's Daily and state news agency Xinhua as "a malignant tumor" in need of eradicating from Hong Kong.

The union's attempts to deflect criticism of its international ties -- deemed "collusion with foreign powers" under the national security law -- met with further scathing responses from both outlets, accusing the PTU of engaging in anti-China and anti-Hong Kong activities.

Organizations accused of such collusion -- including the now-defunct Apple Daily newspaper -- can have their assets frozen under the national security law, rendering them unable to make further payments to staff.

Ivan Choy, senior politics lecturer at the Chinese University of Hong Kong (CUHK), said the demise of the PTU would have a wide impact.

"I believe this is going to have a huge impact on other civil society organizations," Choy told RFA. "If the PTU has no way to hang in there, others are going to find it harder still."

"I am concerned that this will be the start of a domino effect, and that we will see many more organizations disband after this," he said.

'Hong Kong is no more'

A teacher and veteran PTU member who gave only his surname Cheung said he had never thought he would see the end of the union.

"I never thought the PTU would just die," Cheung said. "Everyone expected the Apple Daily's demise, but not such an important group as the PTU, but if they call us a malignant tumor, what can we do?"

"Hong Kong is no more," he said.

The PTU's dissolution comes after around 250 elected, district-level politicians in Hong Kong resigned and dozens of civil society groups disbanded amid an ongoing crackdown on public criticism of the authorities.

Election hopefuls are now required to pass a multi-layered vetting process that includes winning the approval of the national security police before they can even be allowed to run for public office.

More than 120 arrests have been made so far under the law, while incumbent public office-holders will be required to swear an oath of loyalty to Hong Kong and to the CCP.

Among them were 47 former opposition lawmakers and democracy activists, who are now awaiting trial for "subversion" after they took part in a democratic primary in the summer of 2020, in a bid to boost their representation in the city's Legislative Council (LegCo).

Most other former opposition politicians and activists have fled overseas.