The banned but tolerated group had issued on Thursday the call during an inaugural meeting of the National Alliance for Reform and Change, a grouping of activists of different political persuasions united in their desire to see President Hosni Mubarak step down.
The Muslim Brotherhood had invited all of the country's political forces to join the front, but only the centre-right Wafd party sent a representative to the event attended by about 1000 activists.
The organisation has called for nationwide civil disobedience as a means of increasing pressure on Mubarak to end his 24-year rule.
"The Wafd party is honoured to join this alliance," party delegate Mohammed Alwan told participants. He added that his party supported the Muslim Brotherhood's call for civil disobedience to force Mubarak out of office.
"We are not weak, but the government is exploiting our differences," said Magdy Hussein, former editor of the banned Al-Shaab newspaper, mouthpiece of the Islamist-oriented Labour party.
The weight of the new alliance remains limited, with only 19 MPs in the 454-seat parliament, four of them from the Wafd party.
The opposition includes Islamist
and leftist grass-roots groups
The remaining 15 are part of the bloc controlled by the banned Muslim Brotherhood, but all of them entered the house as independents, including the only deputy from the Labour party, whose activities have been suspended.
Nasserist activist and founder of the unregistered Al-Karama party, Hamdeen Sabahi, said he sympathised with the Muslim Brotherhood initiative, although he declined to be part of the new movement.
"The Brothers are the big force that the Egyptian street is in dire need of," he said.
Hundreds of Muslim Brotherhood supporters were arrested during a May crackdown that followed a wave of street protests. Most of them have since been released.
Habib said the new alliance would have a general secretariat and committees.
The 77-year-old Mubarak has yet to announce whether he will seek a fifth six-year term in elections scheduled for September, Egypt's first contested presidential polls.