Hong Kong's leader was challenged to step down Thursday as he clashed with angry pro-democracy lawmakers over the government's controversial electoral reform package, which goes to a vote next month.

Chief executive Leung Chun-ying dodged the resignation question and told legislators the city was at a "critical juncture", urging them to support the roadmap for leadership elections in 2017 -- the first ever public vote for the chief executive.

Pro-democracy lawmakers have vowed to block the package when it goes to the vote in June, calling it "fake democracy" as candidates for leader will be vetted by a loyalist committee, a stipulation laid down by Beijing.

Beijing's decision sparked more than two months of street rallies late last year which brought parts of the city to a standstill.

James To of the Democratic Party asked Leung whether he would step down "to take responsibility" if the package were rejected, a question which Leung did not answer directly.

"If Legco (Legislative Council) members do not endorse the proposal will people ask them to step down?" a riled Leung countered.

Two lawmakers were removed from the heated question-and-answer session for heckling, one holding a yellow umbrella, symbol of the democracy movement, and another shouting "Liar!".

Pro-democracy legislators had also brought cardboard cut-outs of deer, printed with the Chinese character for "horse".

They reflected the Chinese idiom, "Point at a deer, call it a horse", used to refer to deliberate misrepresentation.

Leung argued that the government had "majority support" from residents for the election proposal, citing unspecified opinion polls as backing the plan by 50-60 percent.

The government has asked all 70 Hong Kong legislators to meet with Beijing officials in the southern Chinese city of Shenzhen on Sunday to discuss the plan.

But pan-democrat lawmakers questioned what could be achieved, with both Beijing and the Hong Kong authorities consistently saying that they cannot diverge from the candidate screening policy.

"What are we doing in Shenzhen? There is no room for modifications," pro-democracy lawmaker Ray Chan said in a furious exchange with Leung.

Fifteen pro-democracy lawmakers -- with 12 opting out -- have said they will attend Sunday's meeting with three Beijing officials who deal with Hong Kong affairs.

Authorities have been criticised by pan-democrats for scheduling the meeting on the same day as a march in Hong Kong to mark the anniversary of Beijing's Tiananmen Square crackdown.