President Dmitry Medvedev of Russia has made an outspoken attack on those seeking to rehabilitate Stalin.
Millions of Soviet citizens died under Stalin's rule and Mr Medvedev said it was not possible to justify those who exterminated their own people.
He also warned against efforts to falsify history and defend repression.
Some Russian politicians have recently tried to portray Stalin in a more positive light.
Under President Medvedev's predecessor, current Prime Minister Vladimir Putin, Stalin was often promoted as an efficient leader who turned the Soviet Union into a superpower.
The BBC reports Mr Medvedev made the comments in a videoblog posted on the Kremlin's website.
It appeared on the day Russia is supposed to honour millions of people killed under Stalin's brutal regime which lasted from the late 1920s until his death in 1953.
Mr Medvedev said it was impossible to imagine the scale of repression under Stalin when whole groups of people were eliminated.
However, under Mr Putin, an order was given for school history books to be re-written, highlighting Stalin's achievements.
In Moscow, there is now a Stalin-themed cafe and a metro station with one of Stalin's famous slogans on its walls.