The Muslim Brotherhood party said Tuesday the court's verdicts against former Islamist president Morsi and five other Brotherhood leaders were illegitimate.
The group said in a statement on its Facebook page that it would start a mass protest on Friday against the death sentences.
"The Brotherhood calls on the honorable among this nation to participate in a popular uprising next Friday against the death sentences, detentions, kidnappings, and forced disappearances," it said.
On Tuesday, Cairo's Criminal Court also confirmed death sentences on a number of leading members of Morsi's Muslim Brotherhood group, including its general guide Mohamed Badie. More than 80 accused were sentenced to death in absentia, according to Reuters.
Tuesday's sentencing is still subject to appeal.
The sentences had been pronounced by the court last month but required examination under Egyptian procedures by the country's most senior religious authority, Grand Mufti Shawqi Allam.
Morsi and others, who were freed from internment during the chaos of 2011, had faced charges of conspiring with foreign Islamist groups to organize prison escapes and kidnapping and killing police officers. Egypt's long-time ruler, Hosni Mubarak, was toppled in that uprising.
The Islamist leader became the first democratically-elected president of the country in 2011 after the end of Mubarak's decades-long rule, but was ousted by Egypt's powerful army following a mass uprising against him in 2013. Army head Abdel-Fattah el-Sissi was subsequently elected president.
Criticism against the verdict
"This verdict is a nail in the coffin of democracy in Egypt," Yahya Hamid, a former minister in Morsi's cabinet, told reporters in Istanbul.
Hamid said the trial against Brotherhood leaders had "fallen below all international standards."
Amnesty International described the Cairo trial proceedings against Morsi and other defendants as "grossly unfair."
Turkey last month warned that the Middle East would be thrown into turmoil if Egypt carried out the death sentences.
The US State Department described the Egyptian court's ruling as "unjust."
El-Sissi, while on a visit to Germany earlier this month, was told by Chancellor Angela Merkel that Germany opposes the use of the death penalty.
shs,ipj/mz (Reuters, dpa, AFP, AP)