The centrist Adl Party declared its support for presidential hopeful Hamdeen Sabahi in a press conference on Monday.
During the conference, Sabahi urged political forces that support both the 25 January revolution and the 30 June popular movement that deposed Islamist president Mohamed Morsi to back him in the presidential race.
He also criticised Monday's verdict by a Minya court sentencing over 600 supporters of the deposed president to death, saying that such court rulings are an offense to the judiciary.
He went on to stress that any peaceful political organisation has the right to practice its activities, in reference to another controversial verdict on Monday which disbanded the prominent April 6 Youth Movement on charges of espionage and defaming the state's image.
The Adl Party is the third Egyptian party – after the liberal Constitution Party and the Socialist Popular Alliance Party – to announce its backing of Sabahi, who will be racing against former army chief Abdel-Fattah El-Sisi in the upcoming presidential elections slated for 26-27 May.
The Adl Party was established after the 25 January uprising by former Muslim Brotherhood member Mostafa El-Naggar, who resigned from the party in June 2012.
On Sunday, the Presidential Elections Commission (PEC) announced Sabahi and El-Sisi as Egypt's final contenders for the 2014 presidential poll, the first to be held since Morsi's ouster last July.
Election campaigning will begin on 3 May and last until midnight of 23 May.