Hechmi Haamdi's party, the Popular Petition for Liberty, Justice and Development, finished fourth in the historic elections, after winning 19 seats, including in the second city of Sfax.
"People in Tunisia are congratulating me, because they think what we did is something unexpected and believable," Haamdi, the owner of Pan-Arab television channel Al-Mustakillah, told AFP at his modest London office a few hours before the results were announced on Thursday night.
Haamdi, who has been in exile in London since the 1980s, broke down in tears while recalling the plight of his countrymen under Zine el Abidine Ben Ali, the first leader to be toppled in the Arab Spring.
He also said he was planning to run for the presidency, should Tunisia's new government decide to reintroduce a presidential system.
Speaking from Al-Mustakillah's offices, where he masterminded his party's campaign, Haamdi said: "Our dream is to live in free countries, where we have free elections, dignity, rule of law, democracy and unity amongst ourselves.
"I stood for the things people died for." However, Haamdi's electoral success might be shortlived. The leading party, Ennahda, is refusing to work with his party and six of his candidates' results have been invalidated by electoral authorities due to "financial irregularities".
Ennahda, an Islamist party banned under Ben Ali's dictatorship, won 90 of 217 seats in the new assembly.
Led by Rached Ghannouchi, who also lived in exile in London for more than 20 years, Ennahda are expected to form a coalition with Congress for the Republic and Ettakatol, who came second and third respectively.
Ennahda's candidate for prime minister, Hamadi Jebali, said Thursday his party refused to negotiate with Haamdi's because he was too close to Ben Ali.
Haamdi, an Ennahda member until 1992 when he resigned, said he was "hurt" by Ennahda's stance and said his party would withdraw from the assembly.
"I was hurt that they should refuse to talk to a campaign that represents more than half a million voters," Haamdi said.
Young supporters of Haamdi from his hometown of Sidi Bouzid in central Tunisia smashed windows at the local Ennahda headquarters and threw stones at police.
Haamdi said Thursday he did not condone violence and called upon "the people of Sidi Bouzid and all Tunisians to be united and calm."
Sidi Bouzid is regarded as the birthplace of the national uprising after a young man set fire to himself there in December.
Speaking before Ennahda's declaration on Thursday, Haamdi said he did not share the fears of liberals that Ennahda are moderate in public but radical in the mosques.
"I don't think Ennahda will be a threat in this sense. They have given ample assurances to these people that there is nothing they should worry about," he said.
Other groups are also concerned about Haamdi's past relationship with the dictator.
Houda Trabelsi of the Magharebia information site told AFP that his party's success was "the worst surprise of these results".
He said Haamdi was "a pro-Ben Ali on the political scene. It is shameful. He will never do anything for Tunisia".
Haamdi's Al-Mustakillah channel broadcast the last interview with Ben Ali before the former leader fled to Saudi Arabia.
But Haamdi vehemently denied having a close relationship with Ben Ali.
"Since 1999 Ben Ali never talked to me, I never talked to him. The Eid of last year, I tried to tell him that the situation is deteriorating and he needs to change his way of having the country but he refused to talk to me," he said.
Haamdi, smartly dressed in a light-coloured suit, admitted he contacted the dictator shortly before his regime fell in order to offer him political advice, but was never a supporter of the dictator.
He said he had been too afraid to return to Tunisia during Ben Ali's time.
"If I am someone who is close to Ben Ali, I would have gone to the funeral of my mother who died three years ago, I couldn't do that! I am really hurt," he said.
Haamdi fled Tunisia after the government cracked down on the political opposition and settled in London.
It is not clear how Haamdi has funded his channel, which broadcasts a range of Arabic talkshows via satellite.