The Islamic Action Front (IAF), the political arm of the Muslim Brotherhood, Jordan's largest party, said it had refused to join the 52-member panel and two leading figures, appointed without its consent, would not join any future deliberations.
Prime Minister Marouf al-Bakhit's cabinet announced the creation of the national dialogue committee on Monday in response to a call by King Abdullah to accelerate reforms after weeks of street protests calling for political change.
"We will not engage in an initiative that carries no real dialogue. We demand constitutional reforms and not just amendments to the electoral law. Only the King can manage a national dialogue," said Zaki Bani Rusheid, a leading Islamist.
Islamist, leftist, liberal and even tribal figures have called for the creation of a constitutional monarchy in recent weeks, demanding a government elected by a parliamentary majority rather than appointed by the king.
King Abdullah has called on the committee of lawmakers, former ministers and trade union activists to wrap up their findings on electoral reform within a three-month period.
"We call on you to reach a draft democratic election law that would bring a parliament that represents all Jordanians and plays a leading role in enhancing justice and rule of law," King Abdullah said in a letter to the committee's head, Taher al-Masri.
Labib Kamhawi, a prominent independent figure, who declined the offer to become a panel member, said he had no faith in any reform led by Bakhit who oversaw elections in 2007 which were marred by allegations of vote-rigging.
"I have no confidence in the ability or the intentions of the government to introduce reform that is truly acceptable by the people," Kamhawi said.
"Many of the figures chosen have been part of the past administrations responsible for the mess the country is in now, they cannot be tools of reform."