Two exiled democracy activists wanted by Hong Kong say police in Australia and Britain are investigating fake, sexualised images used to target them in a campaign of harassment.

Former Hong Kong lawmaker Ted Hui, who was granted asylum in Australia, said Australian authorities were investigating a sexualised poster depicting his wife and letters with false claims about him that were sent to Australian addresses earlier this year.

Carmen Lau, who lives in Britain, says her local member of parliament, Joshua Reynolds, alerted her to fake, sexually explicit images of her that had been distributed to her neighbours.

Hui and Lau are among 34 pro-democracy campaigners for whom the Hong Kong authorities last year offered a HK$1 million ($130,000) bounty, accusing them of violating the city's national security laws.

'Humiliation as a tool of political punishment'

Hong Kong has cracked down on dissent in the financial hub under sweeping national security legislation imposed by Beijing after mass pro-democracy protests in 2019.

Lau told Reuters she was "terrified and shocked" by the alleged harassment, adding it was an escalation of a campaign against her since the bounty was issued.

"Sexualised disinformation has long been used to silence women who challenge authoritarian power; this attack follows the same pattern, using humiliation as a tool of political punishment and a warning to others who might speak out against authoritarian regimes," she said in a statement.

A spokesperson for Britain's Thames Valley Police said the reports were being investigated but no arrests had been made.

"The malicious communications are believed to be digitally altered images," the spokesperson said.

Reynolds, the MP for Maidenhead could not be immediately reached outside office hours for comment on the matter, which was first reported by the Guardian.

Hui said he had gone to Australian police after posters depicting his wife's photograph and name, and listing sexual services, were emailed to his former workplace in Australia in August, the month he and his family were granted asylum.

He said he believed "Beijing loyalist groups organised or acquiesced by the Hong Kong regime" had sent the emails, and police were investigating.

The Australian Federal Police had no comment on Hui's account, a spokesperson said.

Australia has raised concerns with China

Australian Foreign Minister Penny Wong raised concerns with her Chinese counterpart Wang Yi in a meeting in July about anonymous letters circulated in South Australia offering rewards for information about Hui and his family.

Those letters were being investigated by the Counter Foreign Interference Taskforce, which includes Australia's intelligence agency and police, for potential breaches of Australia's foreign interference law, a Home Affairs official told parliament in March.

China's Foreign Ministry and State Council Information Office, the Chinese embassy in Canberra, Hong Kong's Security Bureau and the authorities in Macau - where the letters against Lau were allegedly sent from - did not immediately respond to requests for comment.

Beijing and Hong Kong have defended the clampdown on activists, saying it has restored stability to the former British colony.

New Zealand's Security Intelligence Service has also warned of a rise in transnational repression, where individuals viewed as dissidents by a foreign state are targeted for harassment within New Zealand by co-opting others.