Africa's first democratically-elected female head of state, Johnson-Sirleaf, has previously admitted giving money to a rebel group led by Taylor, but said it was meant for humanitarian services.
'Fooled' by Taylor
"If there is anything that I need to apologise for to this nation, it is to apologise for being fooled by Mr Taylor in giving any kind of support to him," Sirleaf said in February.
Taylor is on trial in The Hague on charges of committing war crimes including mass murder, rape and conscripting child soldiers during the interlinked wars in Liberia and Sierra Leone.
He has pleaded not guilty.
Al Jazeera's Haru Mutasa said: "Sirleaf has denied ever being a member of the movement led by the rebel leader.
"[But] if the findings are proved true, this could block a second term in office for her."
Liberia's Truth and Reconciliation Commission does not have the authority to enforce its recommendations but presents them to parliament, which can enact them into law.
The commission was established in 2005 to investigate war crimes committed during Liberia's successive civil conflicts from 1989 to 2003.
Emira Woods, a director at the Institute for Policy Studies in Washington, DC, told Al Jazeera on Tuesday that the information included in the report is not new to most Liberians.
"What is new is the sense that the Truth and Reconciliation Commission may be overstepping its mandate to some extent," she said.
"It is more likely a national elections commission that would give a ruling on who can be the type of candidate for an electoral campaign, and it is ultimately the Liberian people that will have the say in who can legitimately represent them."