The city's Catholic diocese says it will offer help to people arrested or jailed for taking part in next summer's Occupy Central civil disobedience campaign.
A senior cleric said breaking the law, in a non-violent way, in pursuit of fundamental rights, was not a sin.
Vicar-General Michael Yeung Ming-cheung also said the diocese might, in the future, voice support for the campaign, which is seeking "genuine" universal suffrage in the chief executive poll in 2017. But Yeung urged pupils not to take part.
The diocese has published a statement - titled "An urgent call for earnest dialogue and responsible action" - on the front pages of its weekly Kung Kao Po and Sunday Examiner newspapers.
The statement called on the government to immediately launch a consultation over electoral reform, and said acts of civil disobedience could be justified, in certain situations.
They must only be carried out in a peaceful and non-violent manner, and the act "must also itself be an act of conscience directed at preventing or removing grave injustice or violation of fundamental rights".
Yeung expanded on the meaning of the statement: "I believe it is not a sin to join the Occupy Central campaign. It is only an expression, though law-breaking, for civil rights. If any people, from ordinary Catholics to priests, are prosecuted for joining the campaign, the church is obliged to offer support."
Assistance could be in the form of free legal support, or emotional help for people sent to jail.
Yeung said he was worried the key players in the constitutional reform process would not be able to reach a consensus. To avoid that outcome all parties, including the central government, the Hong Kong government and the pan-democrats must start to communicate.
"A delaying tactic is not a tactic," he said, referring to the public consultation on electoral reform which the government has yet to start.
"If the constitutional matter is not resolved, no issues of livelihood can be resolved."
Yeung said the church was not interfering with politics and stressed that it had not taken any side in the Occupy Central campaign.
"But if all means are exhausted and all doors are closed, the church can't stop civil disobedience from happening," he said.
In the statement, the diocese reiterated its call for the chief executive to be directly elected by the one person, one vote method, in 2017. The mechanism for nominating candidates must be "truly democratic".
It demanded all functional constituencies in the Legislative Council be abolished by no later than 2020. All seats in the Legco and the district councils must be returned by universal suffrage.
Meanwhile, executive councillor Bernard Chan said Chief Executive Leung Chun-ying should, at a minimum, give the starting date for the consultation in his policy address in January.
He also said Beijing and pan-democrats should work hard to reach a compromise over the reform proposal.
"If pan-democrats are barred from the election, that implies the proposal would never be passed by the Legislative Council," Chan said.