His comments, broadcast on Facebook and local radio stations, came after diplomatic sources claimed President Rene Preval's Unity Party used its influence to manipulate votes in the legislative elections in its favor.
"The results of the presidential elections matched the people's will. But the results in the Chamber of Deputies and the Senate seem wrong. It seems the people's vote was not respected, because the people protested everywhere," Martelly said in a speech broadcast on Facebook and local radio.
"There were at least 17 lawmakers who were in first place (according to preliminary results released two weeks ago) and are now said to have lost, 17 lawmakers who should have won and did not," he added.
Martelly, who implicitly blamed Unity for the irregularities, said he was seeking "independent verification that the people's vote was respected." He urged Preval to refrain from ratifying vote results provided by the Provisional Electoral Council until the investigation was complete.
Diplomatic officials earlier told AFP Unity was behind the electoral fraud aimed at "retaining control" over Martelly, a relative newcomer on Haiti's political scene whose fledgling Reypons Peysan party scored only three parliamentary seats.
In order to enact the reforms Haiti needs so badly, he will have to forge deals with Unity, which expanded its presence in the lower house Chamber of Deputies, taking 46 of the 99 positions, and gained an absolute majority in the Senate with 17 of the 30 seats.
"There was a lot of pressure" on election officials ahead of the official results unveiled earlier, a European diplomat said. "The international community is surprised by the difference between preliminary results and those unveiled yesterday."
During a visit to Washington, Martelly earlier urged opponents to work with him to rebuild the quake-hit Caribbean nation after being officially declared the winner of last month's run-off.
"We shouldn't see this as an engagement into a fight between each other. We should see it as a collaboration, and this collaboration must be harmonious so it can be fructuous," he told journalists.
In Port-au-Prince, election officials confirmed the former singer and carnival entertainer's presidential victory -- with a resounding 67.57 percent of the vote -- over former first lady Mirlande Manigat.
"We are in a position to choose the prime minister," said leading Unity Senator Joseph Lambert. "We are not going to block the work of the head of state, but he must obtain our support."
Martelly has yet to make an official announcement but observers believe he may ask Unity's Jean-Max Bellerive -- a respected figure well-known to the international community -- to stay on as prime minister and form a government.
As Martelly courted vital foreign investment on his trip to the United States, violence erupted in several towns back home following the overnight announcement of the definitive poll results.
Demonstrators burned vehicles and blocked roads in protests linked to the legislative elections. At least one person was killed but UN police said the circumstances were unclear.
During his three-day trip to the United States, Martelly cut a very different figure from the bad boy entertainer of old and earned a ringing endorsement from US Secretary of State Hillary Clinton.
In addition to lunching with Clinton at the State Department, the incoming Haitian leader met with the chiefs of the Inter-American Development Bank, the World Bank, the International Monetary Fund and the US Chamber of Commerce.
"We were very pleased the financial institutions are open and flexible to new ideas and the interests of the people of Haiti. We are going to pursue them. Haitians do not want handouts. They want opportunities to create wealth," Martelly said.
"Haiti is open to the world, and we invite both tourism and businesses to come and visit as early as possible."
Already the poorest country in the Americas, Haiti was crippled by a January 2010 earthquake that killed more than 225,000 people, displaced 1.5 million, and left the capital in ruins.
The pace of reconstruction under Preval has been slow. Martelly, who takes office May 14, has vowed his first six months will focus on moving hundreds of thousands of quake survivors out of squalid tent cities, tackling a resistant cholera epidemic and boosting agricultural production.
The international community has pledged billions of dollars to speed Haiti's recovery and former US president Bill Clinton, who co-chairs the reconstruction commission, has indicated funds will flow more freely once Martelly has a new government up and running.
"Once I am in office, my government will quickly do an overall assessment to ensure that foreign assistance is going to the people," Martelly said.
The problems are vast: from endemic poverty and corruption to reforming health and education departments largely dependent on foreign NGOs and dealing with a cholera epidemic that has claimed nearly 5,000 lives since October.