Pan-democrats have given a lukewarm response to the central government's approval for all 70 lawmakers to visit Shanghai next month.
Democratic Party chairwoman Emily Lau Wai-hing immediately declined the offer, and at least five lawmakers from the Labour Party and NeoDemocrats have indicated they might also boycott it.
Labour Party lawmaker Lee Cheuk-yan said his party would probably turn down the invitation. The party has four legislators, including Lee.
"Beijing has been taking a strong stance on political reform over the past week. We do not want to create the illusion that we could actually build some consensus with the central government during this trip," he said.
Chief Executive Leung Chun-ying announced on Wednesday that all lawmakers, including radicals and those who had their home-return permits confiscated, had been invited on the two-day trip. He said it might offer the chance to meet central government officials.
Dr Kenneth Chan Ka-lok of the Civic Party was less dismissive of the offer. He said pan-democrats should send some, but not all, representatives to Shanghai - but only if there was definitely dialogue on reform with officials.
"It would offer us a chance to counter the strong words from top officials during the National People's Congress and Chinese People's Political Consultative Conference meeting," he said.
"This kind of conversation is valuable, though we need not expect too much."
Of the 27 pan-democratic lawmakers, 23 will meet today to discuss the issue.
At the heart of the debate on reform is how to put forward candidates for the election of the chief executive by universal suffrage in 2017. Pan-democrats say the public should be able to nominate them. Beijing says this would violate the Basic Law, Hong Kong's mini-constitution.
Some Beijing loyalists urged the pan-democrats to accept the invitation. Tam Yiu-chung, chairman of the Democratic Alliance for the Betterment and Progress of Hong Kong, said doing so would demonstrate seriousness about communicating on political reform.
"It's all about showing mutual respect," Tam said. "If the central government invited you for a meal and you declined and now they welcome you to Shanghai and you decline again, it's useless to talk about other things. [Pan-democrats] should go because there is the chance that we can see mainland officials there."
In January, pan-democrats turned down an invitation for a meal at the central government's liaison office in Western district. Instead, they will have breakfast meetings at the local government's headquarters in Admiralty this month.
Constitutional affairs minister Raymond Tam Chi-yuen said there might be a seminar during the visit at which lawmakers could exchange views on reform directly with central government officials - particularly those in charge of the city's affairs.
"I hope lawmakers will try their best to join," he said.