Spokesman for the Salafist Call group, Yasser El-Borhami, said on Thursday that only a court ruling can determine whether the Muslim Brotherhood is a terrorist group or not.
In December, the cabinet formally declared the Brotherhood a terrorist organisation, accusing the group of links with recent attacks on state institutions and on churches since Morsi's ouster.
El-Borhami added that both his group and its political arm, the Nour Party, reject the cabinet's decision to use the term.
El-Borhami comments came during a conference organised by the Nour Party in Upper Egypt's Aswan to campaign for the newly-amended constitution, which Nour participated in drafting.
"This constitution has preserved both the civil state and the provisions of Islamic law," said El-Borhami, who has been heaping praise on the draft constititon over the past weeks.
He stressed that the drafting of the national charter involved all factions of society.
The referendum, scheduled for 14 and 15 January, will be the first milestone in the transitional roadmap since Mohamed Morsi, the country's first freely elected president, was ousted on 3 July following mass protests against his rule.