Chatham House accused the election officials of not following their own rules, particularly about uploading real-time results.
The Contending parties rejected the announcement of the election results by INEC, and Mr Peter Obi, the Labour Party (LP) presidential candidate, went to court to try to change the outcome.
On Monday, Mr Abubakar Atiku, the presidential candidate for the Peoples Democratic Party (PDP), led a protest against the development, saying he would go to court to challenge the result.
Associate Fellow, Africa Programme, Dr Leena Koni Hoffmann, wrote for Chatham House that the polls opened late, causing many people who wanted to vote to be disenfranchised.
Even though Nigeria has the most extensive voter list in Africa, with 93.4 million voters, less than 25 million valid votes were counted in the 2023 election.
Chatham House said that Nigerians stood in lines in the sun and rain to vote despite frequent fuel shortages, power outages, high inflation, and a painful lack of cash. Still, thousands of voters did not get to vote, and there were a lot of mistakes, and election observers saw violence and intimidation.
Chatham House said less than half of eligible voters could participate in the elections, despite the commission's N305 billion budgetary allocation.
Nigeria's youth seemed energized leading up to the elections. However, their ability to turn out still needed to be improved by how difficult and potentially dangerous they were. It is to cast a vote in Nigeria.
The commission's patchy use of technology in its Bimodal Voter Accreditation System (BVAS) still needed to be closely criticized.
INEC needed to adhere to its own statements and guidelines, which derive from its laws, that election results would be uploaded to its portal using the BVAS directly from the polling unit in real-time for the public's viewing.
Chatham House emphasized the importance of strict transparency by INEC during this crucial phase of electronic results transmission, saying that with only 23% of the public's trust going into the 2023 election, it could not be overstated downplayed.
The organization said that INEC's less-than-ideal performance should be taken seriously because Nigeria's path to recovery and stability must go through accountability and honest elections.
It said that Tinubu would take over a country economically and militarily weakened by his party's rule upon taking office.
Chatham House said leaders would need help handling the vast problems facing Africa's most populous country.
It also said that the Nigerian people, especially the youngest, have shown great strength and have waited far too long for a country that works for them.
Tinubu's party first came into power in 2015 through a campaign of change, and he won in 2023 by running a campaign for renewed hope.
However, many of the issues that worried the Nigerian electorate in 2015 are a more giant headache in 2023, significantly due to the president's self-inflicted fiscal and monetary decisions he will be succeeding in.
In the months leading up to his swearing, according to Chatham House, Tinubu needs to marshal an extraordinary amount of political capital, goodwill, and consensus to redirect and reunite a fractured and volatile Nigeria.
The organization said Nigeria's path to stability and growth requires free, fair, and credible elections. It urged INEC to take urgent steps to address the challenges identified in the 2023 election.