The bloc led by Saad al-Hariri — the son of former Prime Minister Rafik al-Hariri who was killed in a car bomb in February – won all 28 seats in the final voting round, taking its overall total to 72 in the 128-member assembly.
Rafki al-Hariri’s death paved the way for the end of Syria’s long domination of Lebanese politics and galvanised opposition to Syrian influence.
Mr Hariri has pledged to introduce sweeping reforms, saying people had voted for change. He dedicated his victory to his late father: “I owe my father everything.”
The victory means parliament has a majority of lawmakers opposed to Syria’s influence in Lebanon for the first time since the 1975-1990 civil war.
Mr Hariri told a news conference he would issue next week a comprehensive program based on the late billionaire tycoon’s ideas.
“There should be administrative and financial reforms, anti-corruption measures and economic, development and social programs. That’s what we are going to do,” he said.
Sunday’s win makes 35-year-old Mr Hariri a leading candidate for the post of prime minister. He brushed aside questions on future political moves, saying he wanted to consult with his allies first.
Mr Hariri has had no previous political experience but said in a Newsweek magazine earlier this month his father’s death motivated him to achieve what his father had wanted but had not been able to.
A business graduate from Georgetown University in Washington, he is married with two young children.
The pro-Syrian alliance led by Shiite factions Amal and Hezbollah now holds 35 seats in the assembly. An unlikely alliance between Christian opposition firebrand Michel Aoun and long-time friends of Damascus hold 21.
Mr Aoun has already ruled out any possibility of joining a Hariri-led government, accusing his rival of “vote-buying” and pledging to go into opposition.
But there was no immediate word from the Shiite alliance.
The eight-seat majority won by Mr Hariri’s bloc falls short of the two-thirds majority required to unseat pro-Syrian President Emile Lahoud. But Mr Hariri insists he wants to move cautiously on the issue.
“This is an issue that is quite sensitive in Lebanon,” he said. “We will move with the sensitivity that it needs,” he said.
The successful completion of the poll won praise from the US, the European Union and the United Nations.
However, an EU observer mission noted a string of complaints about the conduct of the vote, and called for an urgent overhaul of the sectarian system which reserves half the seats in parliament for the Christian minority, saying it breached its international obligations.
Mr Hariri will now need to use all the business acumen he honed during nine years of running the family empire to put right an embattled economy, burdened by a $US35.5 billion ($A45.7b) debt.
Mr Hariri will also need to face continuing US-led international pressure for the disarmament of Hezbollah’s military wing.
During the campaign, Mr Hariri, who made some electoral deals with Hezbollah, spoke out in favour of the “resistance”, in contrast to Mr Aoun who argued its militiamen should be disarmed in accordance with last September’s UN resolution.