Sadiq Al-Mahdi, who is a former prime minister in the government, has also been pushing for the abolition of the niqab, the female face veils, as a way of 'freeing' Muslim women in Sudan.
Currently, Al-Mahdi leads one of the country's major opposition parties, the Umma Party.
Reacting to the proposals, the Sharī'a Association of Scholars and Preachers of Sudan denounced the comments as "blasphemy" and demanded the opposition leader atone or face trial.
The association is charged with the responsibility of defending Islam, a religion that has strict guidelines for women, especially on dressing.
In recent years, another opposition leader who is a popular Islamic theologian in the Northern African country, Hassan Al-Turabi, was declared an apostate after making statements about women's rights in Islam.
Al-Turabi who leads the Islamist-centred Popular Congress Party (PCP) also said that Muslim women can marry Christian and Jewish men as they are "men of the Book" and that women could lead prayers in mosques and should have equal rights.