Johnson Sirleaf denies the party's allegations that she held inappropriate private meetings with election magistrates before the vote last year.
Liberia's governing Unity Party has expelled the country's outgoing president, Ellen Johnson Sirleaf, whom they accuse of meddling in last year's presidential elections in which its candidate suffered a bruising defeat.
Johnson Sirleaf, a Nobel Peace Prize laureate who has been in power for 12 years, denies the party's allegations that she held inappropriate private meetings with election magistrates before the October 10.
Four other party officials were also expelled, the party said in a statement distributed on Sunday.
"The behaviour of the expelled persons ... constitutes sabotage and undermined the existence of the party," said the statement announcing the decision, which was taken by the party's executive committee late on Saturday.
Former football star George Weah defeated the Unity Party's Joseph Boakai in a landslide, marking the first democratic transition of power in Liberia - a nation founded by freed American slaves - in over 70 years.
Johnson Sirleaf was not allowed to run for re-election due to constitutional term limits. A split between her and Boakai burst into the open during the campaign.
The statement said Johnson Sirleaf and the other members had violated rules, including a requirement to support all Unity Party candidates in elections.
Weah will be sworn in later this month.