Hong Kong should consider adopting a parliamentary system, a prominent democracy scholar has suggested, while a local academic believes a coalition between the chief executive and political parties is more realistic. The city has been witnessing tension between the executive and legislative branches of government, in part because the chief executive is not allowed to hold a party affiliation and thus does not have guaranteed support in the Legislative Council. "If Beijing is worried about unfettered populism and polarisation, switching to a parliamentary system would provide a better and safer model," Stanford University's Professor Larry Diamond, who has advised the World Bank and the US State Department on governance, told the South China Morning Post . He envisions a Legco in which all members are directly elected, and from which a chief minister, taking on functions similar to those of the chief executive, will emerge. The system would require a change to the Basic Law. On the nomination of chief executive hopefuls in the 2017 election, Diamond said some form of public nomination "is the only way to produce a chief executive democratically". Beijing officials have voiced reservations, if not ruled out, the pan-democratic call to allow all voters to nominate candidates. Diamond said international standards of universal suffrage required guaranteeing the free expression of the will of all electors, not just a "special group", like the nominating committee empowered by the Basic Law to choose chief executive hopefuls. He floated two compromise ideas. The first is to expand the nominating committee substantially for the 2017 poll and then eliminate it in 2022. The second idea is to switch to a parliamentary system, which would give the chief executive elected in 2017 a three-year term before filling the position from Legco - which should have gone fully democratic in 2020. Dr Chan Kin-man, an organiser of the Occupy Central pro-democracy movement, said a parliament would save the city from polarisation and let various parties "share power". However, the Chinese University sociologist was pessimistic the system could be implemented. "We once reflected this idea to Beijing, but the discussion didn't go on as they said it was out of the Basic Law's framework." He said a coalition government was possible if the chief executive named members of different parties to the cabinet. An earlier version of this article referred to Larry Diamond as a UN adviser. He has asked us to clarify that he no longer occupies such a role.