CAIRO—Critics of Egyptian President Mohammed Morsi slammed the country's draft constitution after it emerged from a hasty all-night session, with opponents charging the document was a jumbled attempt to impose Islamic law produced by what they called an unrepresentative body dominated by Islamists.

The draft charter, which the president has vowed to put to a national vote soon, emerged a week after Mr. Morsi issued a decree broadly expanding his powers, spurring violent rallies against the president in the worst crisis of...