As officials suggested earlier, the government will not endorse any particular proposal, as this will be the key issue in the upcoming public consultation.

The source said Beijing was insistent that while Hong Kong would pick its own leader in 2017, the electoral process must abide by the Basic Law and the new chief executive must "love the country and love Hong Kong".

These are also likely to be the core principles set out when the National People's Congress Standing Committee meets next month to decide whether to give the green light to reform.

After this decision, the Hong Kong government will launch another round of public consultation by the end of the year.

If the required two-thirds majority is secured to pass the resulting proposal in the Legislative Council - and the chief executive agrees with it - the proposal will be submitted to Beijing for endorsement.

Democracy campaigners said civil disobedience action would "certainly" take place if Beijing ruled out public nomination after an 800,000-strong turnout in the unofficial referendum on the issue and a big turnout in the July 1 pro-democracy march.

Occupy Central co-organiser the Reverend Chu Yiu-ming has already warned that if the reform framework drawn up by the national legislature failed to address calls for "genuine" universal suffrage, there could be strikes.

Federation of Students deputy secretary general Lester Shum also told the yesterday that civil disobedience, such as strikes at universities and road blockades, would "certainly" take place if Beijing ruled out public nomination.

He said he hoped Leung would at least mention "public nomination" or the Alliance for True Democracy's "three track" nomination proposal in his submission.

That proposal, endorsed by 334,000 of the 793,000 participants in the unofficial referendum last month, calls for the public, political parties and a nominating committee to be allowed to put forward candidates.

The alliance argued that its proposal would relieve public fears that the committee - the only body under the Basic Law to enjoy the right to nominate - would screen out Beijing's critics.

Lau Siu-kai, vice-chairman of the Chinese Association of Hong Kong and Macau Studies, said Leung's report was unlikely to dismiss any proposal. But he said discontent was inevitable "because the gap between the two [political camps] is too wide".

Chief Secretary Carrie Lam Cheng Yuet-ngor will unveil a separate report summarising the five-month public consultation that ended in May.

She will attend a special meeting of the Legco House Committee this afternoon before hosting a press conference.

Meanwhile 23 pan-democratic lawmakers issued a joint statement urging Lam to attend Monday's meeting of Legco's constitutional affairs panel.

They said today's two-hour meeting would not give enough time for them to raise questions and reflect the public demand for "genuine" universal suffrage.

Factbox: Five steps to change Hong Kong’s electoral system for the 2017 chief executive and 2016 Legislative Council polls

1. The chief executive on July 15 gives his report to the National People’s Congress (NPC) Standing Committee as to whether there is a need to change the system for the two elections.
2. The NPC’s Standing Committee in August decides on whether the electoral system needs to be reformed. The Hong Kong government then holds a second round of public consultation on the reform proposal by the end of 2014.
3. The government tables its reform package to the Legislative Council for scrutiny. It will need the endorsement of a two-thirds majority of the 70 lawmakers in 2015.
4. The chief executive agrees on the reform package endorsed by the Legislative Council.
5. The chief executive reports back to the NPC’s Standing Committee with the package for approval.