Egypt's legal and parliamentary affairs minister announced his resignation on Thursday, the day after President Mohamed Morsi vowed a government reshuffle to tackle the country's troubled economy.
Mohammed Mahsoub said he was stepping down because "many policies and efforts contradict my personal convictions," according to his letter published on the Facebook page belonging to a leader of his moderate Islamist Wasat party.
He also criticised the government's failure to recover funds allegedly embezzled by members of ousted leader Hosni Mubarak's regime.
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His resignation came two days after that of Morsi's communications minister, Hany Mahmud, who blamed "the current situation in the country".
Mahsoub, Wasat's deputy head, had backed Morsi against the secular-leaning opposition through a deep political crisis over a new constitution that became law this week.
Weeks of protests and violent clashes preceded the referendum this month on the constitution, which was drafted by an Islamist-dominated panel boycotted by Christians and liberals.
In a speech on Wednesday, Morsi hailed the constitution and said he was mulling ministerial changes.
"I will deploy all my efforts to boost the Egyptian economy... and I will make all the changes necessary for this task," Morsi said.