Soon after officials validated the results of the 2 November polls, opposition supporters on Thursday began converging on the Georgian capital of Tbilisi, renewing their demand for Shevardnadze's resignation.
The protesters plan to block the first session of parliament, raising fears the unrest could turn violent.
The Central Election Commission earlier said the pro-Shevardnadze For a New Georgia bloc won the poll with 21.32% votes, ahead of the newly allied Revival Union on 18.84%.
Five opposition representatives on the commission walked out of the stormy session in protest. The commission's head admitted they had to make the best of a bad job.
"Despite all the violations during the election, the mistakes, we did all we could do in our power," Nana Devdariani said.
The United States quickly criticised the vote in Georgia where further trouble could threaten a planned oil pipeline through the country from neighbouring Azerbaijan to Turkey.
"The results do not accurately reflect the will of the Georgian people, but instead reflect massive vote fraud in Ajaria and other Georgian regions," State Department spokesman Adam Ereli said.
Local television showed people starting to travel to the capital to join the demonstrations.
Despite huge protests triggered by the rigged elections, Shevardnadze has steadfastly refused to resign. Even Western observers have described the polls as 'spectacularly' unfair.
"This parliament is illegitimate. It is formed following Shevardnadze's orders," Mikhail Saakashvili, a prominent opposition leader said.