Charles Mok, a pan-democratic lawmaker from the IT sector who met Tam last week, quoted him as saying that the reforms had to be finalised by mid-2016, when the term of the current Legislative Council ends. "I understand he wants to launch the consultation exercise as early as next year."

Emily Lau Wai-hing, the acting chairwoman of the Democratic Party, said the 2016 election must see a substantial reduction in functional constituency seats.

She also advocated the scrapping of the requirement for motions or amendments put forward by members to have the support of a majority both of functional constituency and directly elected lawmakers.

"The ratio of directly elected seats to functional constituency seats must be shifted to at least seven to three or eight to two, otherwise it cannot demonstrate Hong Kong is on its way to universal suffrage by 2020," she said.

While the chief executive election in 2017 would probably be the first to be decided by universal suffrage, there must not be any screening mechanism which excluded all but a few candidates deemed acceptable to Beijing, Lau said. The party will meet Tam on Thursday.

Civic Party chairman Alan Leong Kah-kit insisted his party could accept no less than a "big step forward" in democratic development. He said the pan-democratic camp would try to come up with a common stance.

A bureau spokeswoman said the timing of a public consultation had yet to be decided.

Meanwhile, Civic Party lawmaker Dennis Kwok Wing-hang confirmed he would run for the chairmanship of Legco's legal panel against independent Priscilla Leung Mei-fun today.

His candidacy had been in doubt.