|Ghannouchi, leader of the previously banned al-Nahda party, returned to Tunisia after 20 years in exile [Reuters]
Tunisia's interim government has granted the main Islamist group, al-Nahda, permission to form a political party, the official Tunis Afrique Presse News Agency (TAP) said.
Government spokesman, Ali el-Aryadh, confirmed, "the al-Nahda movement has just been legalised".
Tuesday's decision will allow al-Nahda (The Awakening) to participate in upcoming elections. Al-Nahda was the strongest opposition force before being banned for two decades under toppled President Zine El Abidine Ben Ali's rule.
The movement was founded in 1981 by Rachid Ghannouchi and intellectuals inspired by the influential Muslim Brotherhood born in Egypt.
It was tolerated in the initial years after Ben Ali took power in 1987 but denied legal registration. After a good showing in 1989 parliamentary election, there was a crackdown on its activists and sympathisers.
Ghannouchi returned to Tunisia in January after 20 years in exile in London.
An Islamist-backed coalition won 17 per cent of the vote in 1989 elections, even though the vote was heavily falsified, leading to a crackdown on the movement.
About 30,000 activists and Islamist sympathisers were arrested in the 1990s and many went into exile.
Ghannouchi has said he will not run for the presidency in elections that the interim authority has said will be held by mid-July, but his movement plans to take part in parliamentary elections.
Analysts have said al-Nahda could once again rise as a major political force.