The unprecedented boycott came after pro-democracy lawmakers stood in silent tribute to Zhao in defiance of a warning by Beijing that any official commemoration of the reform leader's death could be unconstitutional.

Zhao, who was ousted for opposing the 1989 Tiananmen Square crackdown, lived out the last 15 years of his life under house arrest. He died Monday, aged 85.

Beijing views Zhao's memory as an internal party matter and Hong Kong is the only place in China where any public commemoration of his passing has been possible.

Mourners have been allowed to pay their respects privately in Beijing at the Zhao home under the watchful eye of security officials.

Dissidents have been tightly watched on the mainland since Zhao's death to prevent any sign of public mourning for the man who once steered the party and whose tearful appearance before students in Tiananmen Square in 1989 was his last public appearance.

Conservative lawmaker James Tien, the chairman of the pro-Beijing Liberal Party, led the walkout by 34 pro-government members.

``We did not have any political considerations,'' Tien insisted. ``We just don't want to see Legco's operations interrupted because of the unruly behavior of some lawmakers.''

The Frontier convenor Emily Lau countered: ``We had no choice but to act in accordance with our consciences.''

She said the aborted Legco meeting was not what they had planned on and that the public would have to deliver a fair judgment on the boycott staged by the pro-Beijing camp.

A source close to the central government said mainland officials were behind the actions of the pro-Beijing camp, but gave no details on how instructions were passed on.

Earlier, Legco president Rita Fan ruled out a call for a minute's silence by saying Zhao's ``contributions to Hong Kong were not significant.''

In 1984, Zhao signed the Sino-British Joint Declaration on Hong Kong's handover.

Wearing mourning colours of black and white, the 25 pro-democracy lawmakers then stood in silent defiance of Fan and heads bowed in memory of Zhao, who is a hero to democracy campaigners in China. Their action prompted all government officials present in the chamber and other lawmakers to walk out.

After 30 minutes, Fan tried to resume the session, but the 34 pro-Beijing lawmakers refused to return, forcing Fan to postpone the meeting until next Wednesday for lack of a quorum.

Tien said his party boycotted the meeting to protest against the ``repeated disruptions'' by the pro-democracy camp during council meetings.

He hopes their boycott will serve as a warning that pro-democracy members have to abide by Legco's rules of procedures and the president's ruling.

``We've always been very passive when they wanted to play games - they start meetings whenever they want and they stop them whenever they want,'' Tien said. ``It's not very fair for us.''

Tsang Yok-sing of the leftist Democratic Alliance for the Betterment of Hong Kong (DAB) said his party was acting to preserve order because of the ``wanton behavior'' of the pro-democracy camp.

``Our boycott has nothing to do with their political stance, but rather on their repeated breaches of the Legco's rules. If we don't stop this wanton behavior, we will disappoint our voters,'' he said.

``We deeply regret that our proposal to observe a minute's silence at today's council meeting to mark the death of Mr Zhao Ziyang was ruled out by the president,'' the pro-democracy camp said in a statement. ``After the minute's silence, we waited quietly for the meeting to resume. Finally, to our regret, the meeting was aborted.''

Democratic Party chief Lee Wing-tat said his party believed that many local people would be in favor of honoring Zhao.

Margaret Ng of the Article 45 Concern Group said they are prepared to receive any punishment from Fan.

``This is a battle between law and conscience. We have no other choice. What kind of cowardice would it be if we refrained from observing a minute's silence? We are prepared to take responsibility for our action and they must take responsibility for theirs,'' she said.

Critics have expressed fears the pro-democracy camp's open defiance on a matter sensitive to the mainland's communist hierarchy could cause Beijing to further tighten its grip on Legco. Beijing fears that too much publicity over Zhao's death could trigger protests.

The party took a low-key approach to Zhao's passing, with the media all but ignoring the news and censors erasing online eulogies. A government spokesman on Tuesday defended its decision to dismiss Zhao, saying he tried to ``split the party.''

cannix.yau@globalchina.com