Proposals for an interim presidential council to manage the nation's affairs returned to the fore this week as a means of pre-empting a return of the Mubarak regime and achieving a degree of national unity.

The Muslim Brotherhood, however, has expressed concern that an unelected presidential body would be both unconstitutional and extremely difficult to implement halfway through Egypt's first post-Mubarak presidential election.

The surprising court verdict on Saturday that acquitted six Mubarak-era police chiefs led to a series of protests in Egypt's major cities.

Despite the life sentences handed to Mubarak and long-time interior minister Habib El-Adly for taking part in the killing of unarmed anti-regime protesters in last year's uprising, the presiding judge in the case said that "concrete evidence" of the police chiefs' culpability had not been forthcoming.

The verdicts have raised protesters' fears about the possible resurrection of the Mubarak regime should Shafiq – seen by many as a "remnant" of the former regime – in this month's presidential runoff vote.

Secular revolutionaries, however, also entertain fears about Muslim Brotherhood candidate Mohamed Morsi assuming power in the absence of guarantees that the Islamist group would not monopolise Egypt's post-revolution political landscape.

Disqualified presidential candidates Hamdeen Sabbahi and Abdel-Moneim Abul-Fotouh – who came in third and fourth respectively in last month's first-round vote – held a meeting on Sunday at which they expressed their tentative support for the proposed presidential council.

A spokesman for the Salafist Nour Party on Monday also said his party supported the presidential council initiative, but only if it came as a result of consensus among political forces.

The Brotherhood, meanwhile, whose presidential candidate won first place in the first round of voting late last month, has reiterated its position that the proposed presidential council would be unconstitutional since members would not be elected.

Brotherhood spokesman Mohamed Hussein said on Monday that it would be "difficult" to put the proposal into practice since Egypt's ruling military council has been firm about holding scheduled presidential elections as the sole means through which it would hand over executive authority.

The presidential council initiative was first tabled by Mohamed ElBaradei's National Association of Change only days after the ouster of longstanding president Hosni Mubarak. The idea came up again during November's violent clashes on Cairo's Mohamed Mahmoud Street, when Tahrir Square protesters called on prominent political figures to form a presidential council mandated with stopping the carnage.

The initiative was supported at the time by a number of revolutionary youth groups, but did not survive subsequent negotiations with the ruling military council.

In late April, revolutionary forces rejected Shafiq's entry into the presidential race, despite the ratification of a Political Disenfranchisement Law banning Mubarak regime figures from assuming government positions. Shafiq, however, ended up coming in second in the first round of voting, meaning that he will take on the Brotherhood's Morsi in this month's runoff vote.

An alternative to the proposed presidential council would be an agreement to form a "presidential team" with Sabbahi and Abul-Fotouh serving as Morsi's vice presidents as a quid pro quo for supporting Morsi in the runoff. As of press time, Morsi, Sabbahi and Abul-Fotouh were holding meetings on the issue with prominent activists in Cairo.

Sameh Ashour, head of the ruling military council's advisory board, said after meeting with military leaders on Monday that the presidential race would continue as planned, dismissing calls for the proposed presidential council on the grounds that such a council would be unconstitutional.