BERLIN — As Russia gets ready for another round of elections whose outcomes are in little doubt, Mikhail Gorbachev, the Soviet Union’s final leader, condemned on Tuesday what he called “imitation” democratic institutions in his country, and he said that Russia’s current leaders should not expect to maintain support forever.

Twenty years after Gorbachev presided over the dismantling of the Soviet Union, he has become increasingly critical of Russia’s government. Since Prime Minister Vladimir Putin announced in September that he planned to move back into the presidency, the country’s top job, Gorbachev’s criticism has only grown.

“We must ensure that all democratic institutions really function, not as an imitation, as is now the case. The parliament, justice, the courts,” Gorbachev, 80, said in an interview.

Russia will elect its parliament Dec. 4; in March it will pick a new president. And although Putin’s United Russia party will undoubtedly retain legislative power, “it could happen that before the presidential election the situation could shift somewhat,” Gorbachev said.

Small cracks have opened in Putin’s once unassailable hold on power, even though few credible challengers exist.

On Sunday he was booed at a martial arts fight in Moscow by a large swath of the 20,000-plus crowd, a rarity in a country more accustomed to resigned acceptance of Putin.

His poll numbers have been slipping, along with those of his party.

Gorbachev, without mentioning Putin by name, brought up the example of British Prime Minister Margaret Thatcher, who presided over three Conservative victories before being deposed in 1990 by a rebellion among the ranks of her own party.

“There are many things that cannot be foreseen,” Gorbachev said. “The political leaders are losing prestige and authority.”

Grumbling about Putin’s rule has increased since he announced in September that he planned to take back the presidency from his political ally Dmitry Medvedev, who has held the job since 2008, when Putin was forced by term limits to take a break.

The decision raised the prospect that Putin could remain in the Kremlin for another 12 years, putting him second only to Josef Stalin in the length that any one leader has dominated the country’s politics in recent times.

Gorbachev, much admired in the West for bringing about the largely bloodless fall of the Iron Curtain, is far more influential abroad than he is at home, where many resent him for the economic chaos that accompanied the Soviet Union’s end.

In March he held his star-studded 80th-birthday extravaganza in London’s Royal Albert Hall, not in Moscow, much to the amusement of many Russians.