Speaking Tuesday at a round table discussion devoted to the 15th anniversary of Putin's first presidential election victory in 2000, Alexei Kudrin predicted that Russia's struggling economy will continue on its downward trajectory.
"We will emerge from the crisis into economic stagnation. Structural reforms were not done in time. This is the most serious challenge facing the president - a stagnating economy at least for the next five years," he said, according to a report from Russian business news agency, RBC.
"From 2012 to 2018 economic growth will be 1.5 percent [per year], in the best case - 2 percent," he added, warning that Russia was "stuck."
Kudrin served as Russia's Minister of Finance from 2000 to 2011 and during his time in office was seen as a reformer and responsible for reducing Russia's foreign debt. However, in 2011 he was asked to resign by the then Russian Prime Minister Dmitry Medvedev after a reported disagreement over economic policy.
His comments are a rare display of criticism from a former Putin, whose domestic standing is still strong despite the international criticism, a domestic economic crisis caused by the decline in global oil prices and sanctions over its role in the conflict in east Ukraine.
Independent Russian polling body, the Levada Center, put Putin's approval ratings at 85 percent in March and the figures have remained consistently high despite the fall in the ruble and rampant inflation hurting Russians' disposable income.
Kudrin said Putin could use his popularity to drive through reforms that he has promised but has apparently been slow to deliver.
"Global leaders' high ratings are a basis for trust and to conduct reforms," Kudrin said, adding "If this rating is not used to push through reforms it will be just a rating for the sake of a rating."
The Russian central bank predicted in December that the economy could contract 4.6 percent this year so whether Putin's approval rating can withstand the expected recession this year is uncertain.