In a final declaration issued in London on Sunday, the groups addressed the United Nations, saying the global body was responsible for restoring Libya's constitution.
The charter was drafted in 1951 as part of a UN resolution -but al-Qadhafi froze it after assuming power in a military coup and replaced it with martial law.
"Bringing back constitutional legitimacy to Libya is a major factor towards building a stable political life," the declaration read.
Demonstrators apparently recruited by the Libyan embassy in London entered the hotel where opposition members were meeting to try to disrupt the proceedings.
Carrying the green Libyan flag and chanting pro-al-Qadhafi slogans, the protesters - mainly students - were asked by police and hotel security to leave the hotel.
Some 200 people also rallied on Sunday outside the embassy, waving Libyan flags and holding placards bearing Gadhafi's photo. They shouted "Look for peace together" and "Work for democracy together" in Arabic.
"Bringing back constitutional legitimacy to Libya is a major factor towards building a stable political life"
"We believe in democracy for all people," said demonstrator Mostafa Ywali.
He said opposition groups were holding a meeting in London "to make trouble in Libya."
Some 600 Libyan students were expected to hold a pro-al-Qadhafi demonstration in front of the Libyan embassy on Monday to voice support for the regime.
Conference participants said the students were being threatened with having their scholarships cut if they did not join the demonstration.
While agreeing on the necessity of a government change in Libya, al-Qadhafi's opponents in exile could not agree on the best strategy to make that happen.
But participants in the London conference proposed setting up a new satellite television network to use to encourage Libya's silent majority to stage a series of protests that might lead to a popular uprising.
The 200 participants also vowed to take al-Qadhafi, his family and all his aides to the international court to try them for war crimes.
Those who boycotted the conference accused participants of using unrealistic language.
"How would al-Qadhafi step down? It's not realistic," leading opposition figure Ashur Shames said. "They (the conference) have no mechanism to oust al-Qadhafi unless they seek international pressure, or by the use of force."
Libya's Muslim Brotherhood group also stayed away from the conference, claiming the only way to bring about change was to reform the regime from within.
Son Seif el-Islam al-Qadhafi is
seen as a likely successor
"There are people inside the government and the regime who are advocating negotiation with the opposition ... we want to encourage those people to be more dominant," Shames said.
He was referring to Seif el-Islam al-Qadhafi, Muammar al-Qadhafi's son, believed to be the likely successor to the Libyan leader.
Muslim Brotherhood member Nasser al-Manie called opposition demands "slogans that might be exploited by some parties to put pressure on Libya".
One of Libya's oldest Islamic groups, the Muslim Brotherhood has around 90 political prisoners detained in Libya.
Al-Qadhafi's son has promised to work to free them.
Al-Qadhafi has ruled Libya since
staging an army coup in 1969
But for some opposition members meeting here, it was too late for this government to reform.
"There is no other option: al-Qadhafi must go and the constitution must come back," Salem Mohammed, a senior member of the National Movement, said.
The conference received e-mails from Libyans purportedly from within Libya. One addressed the groups who boycotted the gathering, warning them not to believe that al-Qadhafi was capable of reform.
"Al-Qadhafi talks and lies and when he lies he believes it himself," said an e-mail from someone who gave his name as Zaki Nagi. "Be careful my brothers, so you won't be losers in the end."