Dmitry Medvedev, the Russian prime minister, has called for the three jailed members of the feminist punk band Pussy Riot to be freed.

But Pussy Riot's supporters quickly dismissed the prime minister's statements, noting his long history of appealing to Russia's more liberal demographic while failing to follow through on delivering results.

In televised remarks about the band on Wednesday, Medvedev said he was "sickened by what they did, by their looks, by the hysteria that followed what had happened". Three members of the radical anti-Kremlin punk collective were sentenced to two years in prison last month on charges of hooliganism motivated by religious hatred after performing a song criticising Vladimir Putin in Russia's official cathedral. The case sparked a global outcry and highlighted the crackdown on the opposition inside Russia.

But Medvedev said he believed the women should be freed early. "The prolongation of their incarceration in the conditions of jail seems to me to be unproductive," he said. "A suspended sentence, taking into account time they have already spent [in jail], would be entirely sufficient."

The three women – Maria Alyokhina, Yekaterina Samutsevich and Nadezhda Tolokonnikova – have been jailed since their arrest in early March. They remain in a pre-trial detention centre in Moscow as they wait for their appeal to be heard. The appeal is due to start on 1 October.

"This well-known group of girls has been in jail long enough," Medvedev said, calling the time they had already spent in detention a "very serious punishment regardless of the sentence".

Medvedev – who forwent seeking a second term as president to allow his mentor, Putin, a free run – has long sought to portray himself as a liberal reformer. As president, he had vowed to reform Russia's culture of "legal nihilism", building on his career as a lawyer. Yet critics of the government note that his numerous statements on various legal cases – including the need to fully investigate the death in custody of the lawyer Sergei Magnitsky – have yielded no results. He ceded the presidency in May to Putin amid unprecedented anti-government protests.

"Medvedev has already spoken about several criminal cases and we know what the results have been," said Nikolai Polozov, a lawyer for Pussy Riot. "I agree with what he said – that they should be let out. But considering all the other awful propaganda against our clients, it seems his voice will not be heard. This is an attempt to save face."

A popular programme on state-run television said in a broadcast late on Tuesday that the Pussy Riot women were doing the devil's work, and were the brainchild of the London-based oligarch and Kremlin foe Boris Berezovsky. Berezovsky denied the accusation.

Pussy Riot's supporters accuse Putin of personally orchestrating the campaign against the band. The women sang a song that begged the Virgin Mary to rid the country of the powerful leader.

During the trial, Putin called for the women not to be judged "too harshly". The court handed them a two-year sentence instead of the maximum seven years or the three years requested by the prosecution.

Both Putin and Medvedev said they had no intention of interfering in Russia's notoriously politicised court system.