Hong Kong is set to introduce a controversial bill on Wednesday that would make disrespecting the Chinese national anthem a crime punishable by up to three years in prison, raising fresh fears about freedom of expression in the city.

Chinese authorities have sought to instil greater patriotism in the former British colony at a time of heightened tension between democracy activists and forces loyal to Beijing, with some in Hong Kong advocating independence from China.

Booing the anthem at football matches in the Chinese-ruled territory has emerged as a form of political protest in the past few years, seized upon by young people keen to demonstrate their frustration at Beijing’s perceived creeping influence.

Besides imprisonment, the measure would fix a maximum fine of HK$50,000 ($6,373) for those who publicly and intentionally disrespect the anthem, the March of the Volunteers.

It also extends to schoolchildren, including pupils of international schools, who would be legally required to learn the anthem.

Secondary school teacher Simon Hung, 36, said: “I think teachers would feel worried about this proposal, because if we allow this government to pass a law to instruct the teachers what to teach, well, this time it is for the national anthem, maybe next time it could be other things.”

The anthem proposal is expected to pass easily when it comes to a vote – probably in the coming months – because the opposition does not have enough seats to block routine legislation.

The global financial hub returned to Chinese rule in 1997 under a so-called “one country, two systems” formula that promises the city a high degree of autonomy, including freedom of expression.

Hong Kong has already outlawed the desecration of national flags and emblems, which can attract jail terms of three years.

Calls for outright independence are a red line for China’s Communist party leaders, who deem Hong Kong an inalienable part of the nation.

But many young people in Hong Kong have become increasingly angered by what they see as China’s encroachment on the city’s culture and autonomy, with some advocating “localism”, or a Hong Kong identity, rather than a Chinese one.

“We have no sense of belonging to China at all,” one football supporter said. “Even people I know who are born since 1997, they still think they are HongKongers, but not Chinese.”

In 2017, mainland China adopted a law banning disrespect for the anthem. A similar measure is being reviewed in Macau, also designated a Chinese special administrative region. Opponents and press freedom advocates in the world’s largest gambling hub have criticised a provision for authorities to seek media assistance in anthem promotion campaigns.