A branch of the April 6 Youth Movement, once a leading revolutionary youth group and now outlawed by interim authorities, said on Wednesday it opposes former army chief Abdel Fattah El-Sisi's presidential candidacy but has not yet decided whether or not to boycott the upcoming poll.

El-Sisi, whose popularity skyrocketed since he led the ouster of Islamist president Mohamed Morsi last summer, is highly tipped to win the 26-27 May presidential election, running against only one rival, Hamdeen Sabahi, who came third in the 2012 elections that Morsi won.

An in-house poll showed that members evidently oppose El-Sisi, with some either backing Sabahi or pondering a boycott, the April 6 Democratic Front said in a statement, adding that the group may boycott or throw its weight behind leftist Sabahi.

"So the group declares liberty to its members to decide on their line on the presidential elections," the front said, announcing the launch of a new campaign called "Against You" opposing El-Sisi and what it says is the return of the "repressive regime" of former autocrat Hosni Mubarak.

An Egyptian court last week banned the April 6 movement -- one of the youth groups that led the 2011 uprising against autocrat Hosni Mubarak. The ruling stemmed from a private lawsuit accusing the group of defaming the country and colluding with foreign parties.

April 6 had opposed Islamist president Morsi and supported his ouster last summer, but also spoke out against the interim authorities that replaced him, protesting their crackdown on dissent. The group has frequently accused the interim leaders of quashing freedoms and giving the police a free rein.

Local media has cast April 6 as a treasonous movement that answers to foreign agendas.

New-York based Human Rights Watch condemned the ban as an "escalation in the government’s campaign against all peaceful opposition."

April 6 and its offshoot have vowed to appeal the ban.

In December, leading members of April 6 - Ahmed Maher, Mohamed Adel and longtime activist Ahmed Douma - were sentenced to three years in prison on charges including protesting illegally. Their appeals were rejected last month.

Authorities have already outlawed Morsi's Muslim Brotherhood movement, waging an unrelenting crackdown against the group that has killed hundreds and jailed thousands of others.