HONG KONG (Reuters) - Hong Kong pro-democracy lawmaker "Long Hair" Leung Kwok-hung has been charged with failing to declare a donation of HK$250,000 ($32,000) from a media tycoon and outspoken critic of China, the Chinese-ruled city's corruption watchdog said on Thursday.


The charge comes at a time of mounting political tension in Hong Kong with a growing trend of radical activists forming political groups and staging disruptive protests calling for democracy for Hong Kong or independence.


The Independent Commission Against Corruption (ICAC) said Leung, 60, a member of Hong Kong's Legislative Council and a strident China critic who frequently heckles officials, was charged with one count of misconduct in public office.


It said Leung concealed the payment from the Legislative Council in May 2012 from Jimmy Lai, the owner of pro-democracy Next Media Ltd which publishes the Apple Daily tabloid.


"The charge comes really close to the Legislative Council election," Leung told Reuters. "It might hurt the images of pan-democrats before the election."


He was not able to comment further and the ICAC did not give details of the payment. He is due to appear in court on Friday after being released on bail.

The idea of Hong Kong independence is anathema to Communist Party rulers in Beijing, who fear any separatist or sweeping democratic demands spilling into China, undermining their power.

Hong Kong returned from British to Chinese rule in 1997 under a "one country, two systems" formula, allowing it freedoms not enjoyed on the mainland. The Legislative Council election is in September.

(Reporting by Farah Master and Sharon Shi; Editing by Nick Macfie)