* Nobel prize winner quit government over crackdown
* Hearing due on Sept. 19, ElBaradei unlikely to attend
* Case brought by an Egyptian law professor
Mohamed ElBaradei, Egypt's former vice president, will be sued in court for a "betrayal of trust" over his decision to quit the army-backed government in protest at its bloody crackdown on the Muslim Brotherhood.
The case, brought by an Egyptian law professor, will be heard in a Cairo court on Sept. 19, judicial sources said on Tuesday.
It points to the prospect of a new wave of politically driven lawsuits being brought to court following the downfall of President Mohamed Mursi, whose supporters brought a raft of cases against opposition figures during his year in power.
The cases, many of them for "insulting the president", have been criticised by anti-government activists as a form of political intimidation.
ElBaradei, former head of the U.N. nuclear agency and co-leader of the secular National Salvation Front grouping, was the most prominent liberal to endorse the military's overthrow of President Mohamed Mursi on Aug. 3 following mass protests.
But he resigned on Aug. 14 after security forces used force to crush the protest camps set up by Mursi's Muslim Brotherhood supporters in Cairo, killing hundreds of people.
The military's intervention against Mursi has polarised public opinion in Egypt. Around 900 people have died in violence across the country over the past week.
The case was filed by Sayyed Ateeq, a law professor at Helwan University.
"He was appointed in his capacity as a representative of the NSF and the majority of the people who signed the Tamarod declaration," he told Reuters, referring to the coalition that led the anti-Mursi protests.
"Dr. ElBaradei was entrusted with this position and he had a duty to go back to those who entrusted him and ask to resign."
The media head of the Dostour party, founded by ElBaradei, condemned the case, saying it had no legal grounds and was only aimed at tarnishing ElBaradei's image.
Khaled Daoud said the lawyer who brought the case "set a precedent that harms Egypt's reputation abroad, when a politician is prosecuted just for resigning from his post, something that has never happened before in any country in the world".
Ateeq said that, if found guilty, ElBaradei could face a three year jail sentence. But a judicial source said the maximum sentence that could be imposed in a case of this kind was a fine and a suspended jail term.
ElBaradei left Egypt earlier this week for Europe and is unlikely to attend any hearing in this case.
The lawsuit follows a wave of arrests of Muslim Brotherhood leaders in recent days and a decision by the public prosecutor to charge Mursi, who is being detained in an undisclosed location, with inciting violence.
Khaled Dawoud, a former aide to ElBaradei who joined him in quitting the National Salvation Front following the crackdown, said any decision to try the Nobel peace prize winner would be a political escalation against critics of the military crackdown.
"If this case against ElBaradei is true then it is a major escalation showing that things are getting very polarised. You're either on this side or on that side," he told Reuters.