Thousands of Russians have rallied in Moscow and St. Petersburg in the last two days, facing off against tens of thousands of police and Interior Ministry troops. Hundreds of protesters have been detained in both cities.
Gorbachev told the Interfax news agency that authorities must hold a fresh election or deal with a rising tide of discontent.
Prime Minister Vladimir Putin's United Russia party won less than 50 percent of Sunday's vote, a steep fall from its earlier two-thirds majority, according to preliminary results. But opposition parties and international observers said the vote was marred by vote-rigging, including alleged ballot-box stuffing and false voter rolls.
"More and more people are starting to believe that the election results are not fair," he told Interfax. "I believe that ignoring public opinion discredits the authorities and destabilizes the situation."
Gorbachev added that authorities "must admit that there have been numerous falsifications and ballot stuffing."