The Maldivian Democratic Party made the accusation after the court ordered the Elections Commission to re-register some voters, a process the party says can't be completed in time for the Oct 19 revote.
The Supreme Court this week annulled results of the Sept. 7 first round of voting, agreeing with a losing candidate that the election was flawed. The United Nations, United States and European Union had hailed the voting as free and fair.
Yaamin Abdul Gayoom, brother of the country's longtime autocratic leader Maumoon Abdul Gayoom, finished second and was to face Nasheed in a Sept. 28 runoff.
However, businessman Qasim Ibrahim, who finished a close third, complained that he was denied a runoff slot because the voter registry included made-up names and the names of people who are deceased.
The difference between the second and third place candidates was about 2,700 votes.
The Maldives became a democracy in 2008 and Nasheed, who became president in the country's first multiparty election, resigned last year amid public protest and sliding support from the military and police over his order to arrest a senior judge.