"Police officers enjoy the same right of freedom of expression as ordinary citizens do, but their freedom comes with restrictions," Cheung said, referring to Police General Orders.

The orders say officers shall not take part in political activities, and "at all times abstain from any activity which is likely to interfere with the impartial discharge of duties, or which is likely to give rise to the impression amongst ... the public that it may so interfere."

Cheung's comments came as pan-democratic lawmakers lodged a petition on Friday urging Police Commissioner Andy Tsang Wai-hung to clarify whether some officers, by signing the anti-Occupy campaign, had breached their code of conduct.

Occupy Central organisers warn they will paralyse the city's business district if the government fails to give people "genuine" universal suffrage to elect their leader in 2017.

James To Kun-sun, vice-chairman of the Legislative Council's security panel, said officers, especially senior ones, should not express views in a high-profile manner that would make the public feel they would be unfair or biased in enforcing the law.

He urged those in the higher ranks to clarify the issue to frontline officers.

Meanwhile, the Alliance for Peace and Democracy launched an online platform for its anti-Occupy signature campaign yesterday. The campaign began on July 19 and will end on August 17.

The campaign requires those signing to provide a full identity card number, although organisers admit having no measures to guard against repeat signing. By 10.30pm yesterday, 12,067 names had been gathered online, and 1.05 million names at physical stations.

Executive Councillor Bernard Chan said he had signed for the campaign, noting that Occupy was not the best way to fight for universal suffrage.

July 1 protesters make their point outside Hong Kong police headquarters

A month since they were arrested, some of the July 1 protesters gathered outside the Wan Chai police headquarters yesterday to demonstrate their commitment to peaceful civil disobedience.

About 200 people attended the rally - including many of the 511 who were arrested following the Chater Road sit-in. The Civil Human Rights Front organised the rally to inform the public of their peaceful intentions and to reject claims that the Occupy Central movement is violent.

Among the protesters was Uncle Wong, who, at over 80, was one of the oldest people arrested on July 1. He said: "I arrived at Chater Road [that night] and wanted to support the children. I was really happy that there are youngsters with even more passion and courage to fight for democracy, so I stayed."

Wong said he would take part in the peaceful protests again. "I didn't do anything wrong. Even if I am put in prison, I'm fine with it," he said.

Johnson Yeung Ching-yin, convener of the Civil Human Rights Front, said: "In the past few months, there have been many groups coming out to slander Occupy Central as violent, creating chaos in Hong Kong. Through this rally, we want to get our protesters to explain their experiences and to have scholars summarise what happened on July 1 and 2.

"Our civil disobedience and Occupy Central will be held in a peaceful, non-violent manner."

Those who took part in civil disobedience were both law-breakers and the most law-abiding citizens, said University of Hong Kong philosophy professor Timothy O'Leary. "Students break the law because they respect the law," he said. "[They are people] who believe in a better law."

Democratic Party heavyweight Martin Lee Chu-ming said democracy would come sooner or later to Hong Kong and China. To deny citizens' rights to democracy would be "veering off-course from the blueprint of Deng Xiaoping , " he said.