A hero to some and a pest to others, maverick Hong Kong lawmaker "Long Hair" Leung Kwok-hung is universally recognised as the most outspoken critic of the city's ruling business elite.

With his trademark ponytail and Che Guevara T-shirts, he has cut a defiant figure in the Asian financial centre's legislative assembly since winning a seat representing the gritty New Territories East electorate in 2004.

But his activism has already landed him in jail four times, and a new conviction, handed down in March for disorderly behaviour and causing criminal damage at a public forum, could threaten his career as a lawmaker.

He was sentenced to two months jail, enough to see him stripped of his seat and barred from contesting September polls.

The 56-year-old former construction worker says he is more than just a professional protester, and has vowed to fight his conviction or serve his sentence in time to legally nominate for re-election.

"It is totally wrong to suggest I only protest. I can deliver speeches, which I have done day-in, day-out in the chamber," the second-term legislator says at his office in the city's equivalent of parliament house.

His desk has a wooden plaque that says "Mr Long Hair", and his office is crammed with books and Che memorabilia including posters, mugs and a "limited edition" doll.

The late Cuban Marxist revolutionary is also emblazoned on Leung's silver minivan in the parking lot. The vehicle's number plate, DONALDPK, is an insult directed at the city's bow-tie wearing chief executive, Donald Tsang.

Leung can often be spotted in the regional financial hub's glittering business and shopping districts armed with a loud hailer and cigarettes, campaigning for greater Chinese democracy and better rights for the poor.

His performances in the assembly are just as vocal, and frequently end in him being ejected from the chamber. He comes armed with props such as balloons and vegetables, which he has been known to hurl at government officials.

"You eat rice but don't know how expensive it is ... Why can't you have some mercy on the poor?" Leung asked Tsang during a heated debate about the minimum wage in 2008, before presenting the chief executive with a banana.

In March he gatecrashed the convention centre where the 1,200-member electoral committee -- packed with pro-Beijing business and political elites -- were selecting a new business-friendly chief executive to replace Tsang.

Wearing a yellow emperor suit, a pig-wolf mask and holding a papier-mache Chinese tank, he shouted "I am the king and kingmaker" as the delegates arrived to cast their votes behind closed doors.

The high school graduate made his presence felt from day one of his political career, when he attended the swearing-in ceremony in a black T-shirt to commemorate the 1989 Tiananmen Square crackdown.

When he was called to take his oath, he raised his fist and shouted "Long live democracy! Power to the people!"

He earned his latest conviction after he led a small group of demonstrators into a public forum at Hong Kong Science Museum in September that was discussing proposals to scrap by-elections.

The protesters seized the stage, clashed with museum staff and damaged public property.

Leung defends what he calls his "visual and sensational" style.

"If you want to draw the attention from the crowd, you need to climb the ladder to let other people see you. Otherwise, it is a waste of time," he told AFP in English, wearing a T-shirt with a "21st Century Socialism" logo, khaki pants and sandals.

"If you live in a deformed society, you need to be deformed first."

Leung is a founding member of the League of Social Democrats, a party at the radical end of the pro-democracy spectrum in the former British colony.

Hong Kong, a city of seven million people, reverted to Chinese rule in 1997 under a mini-constitution that guarantees its basic freedoms while ensuring that ultimate power rests with the communist central authorities in Beijing.

The "One Country Two Systems" arrangement has led to great wealth accruing to a handful of family business empires in one of the most laissez-faire economies in the world.

But the city's success has come at a high price for the disadvantaged, who struggle with some of the world's highest property prices and limited social welfare.

Leung says he knows what it's like to be poor, having been raised by a stepfamily after his father abandoned his mother, who was then forced to work as a maid for a wealthy British family to make ends meet.

Despite his outsider status, he says he is not daunted by the challenge of transforming China's most capitalist territory into a socialist democracy.

"I really believe Asia will change. China will change, Hong Kong will change. I believe in people," he says.