Abdel Aziz al-Hakim, the chief of the Supreme Council for the Islamic Revolution in Iraq (SCIRI) said on Friday that the new constitution also must be ratified through a nationwide referendum.
"The drafting of a permanent constitution for the country must be done by a panel elected by the Iraqi people," al Hakim said at a mourning ceremony for his brother, Ayatollah Muhammad Baqer al-Hakim, killed last month.
"It must be ratified through a nationwide referendum," Hakim told a crowd of 10,000 people who had gathered to mourn the slain cleric.
SCIRI has meanwhile criticized the new US draft resolution on Iraq since it gave no deadline for a withdrawal of coalition forces from the country.
Reda Jawad Taqi, a SCIRI representative said the draft was "weak" because it does not include a deadline and a timetable for the withdrawal of coalition forces.
One of Iraq's key Shia political parties, SCIRI also demanded a "timetable for the transfer of power from the US forces and the occupation administration led by Paul Bremer to the Iraqi people."