Nadezhda Tolokonnikova says feminist punk band's predicament shows how freedom is being taken away from all Russians

On the eve of a court verdict that could see three members of the punk band Pussy Riot jailed for participating in a protest in a cathedral, one of the women warned that the trial was a sign that freedom was disappearing in Vladimir Putin's Russia.

"I hold no spite," Nadezhda Tolokonnikova wrote in a letter to supporters (in Russian) passed to one of her lawyers. "I have no private spite. But I have political spite.

"Our being in jail is a clear and distinct sign that freedom is being taken away from the whole country," she wrote. "And this threat of destruction of the liberating, emancipatory forces of Russia is what makes me angry."

The three band members – Tolokonnikova, Maria Alyokhina and Yekaterina Samutsevich – will hear the verdict against them on Friday afternoon. Prosecutors have asked the judge to jail the women for three years, arguing that they should be isolated from society after performing an anti-Putin punk prayer in the Cathedral of Christ the Saviour in Moscow in February. They are accused of hooliganism motivated by religious hatred.

Formed shortly after Putin announced his intention to return to the presidency last September, Pussy Riot say their performances, including that of the "punk prayer", are motivated by anger at Russia's lack of freedom and democracy, as well as its sexism. "The second wave of feminists said: the personal is political," Tolokonnikova wrote. "The Pussy Riot case has shown that the personal problems of three people, charged with hooliganism, can give life to a political movement."

She marvelled at the international attention the case has received, with musicians including Madonna and Björk coming to Pussy Riot's support. Sir Paul McCartney added his voice on Thursday, saying in a statement on his website addressed to the three women: "I would like you to know that I very much hope the Russian authorities would support the principle of free speech for all their citizens and not feel that they have to punish you for your protest.

"I hope you can stay strong and believe that I and many others like me who believe in free speech will do everything in our power to support you and the idea of artistic freedom."

Dozens of protests are planned in cities around the world to coincide with the verdict reading on Friday.

"It's still hard to believe this is not a dream," Tolokonnikova wrote.

The trial comes amid a wider political crackdown on the opposition movement borne of fears over Putin's return to power. A series of laws targeting demonstrations, non-governmental organisations and the internet were adopted this summer, and charges have recently been brought against opposition leader Alexey Navalny.

The opposition have called for supporters to don balaclavas, part of Pussy Riot's signature look, at a protest at the court on Friday. Another protest is planned for Sunday.

"Something unbelievable is happening for modern Russian politics: the demanding, stubborn, authoritative and consistent impact of society on the authorities," Tolokonnikova wrote. "I'm grateful to everyone who has said: Freedom for Pussy Riot! We are witnessing a big and important political event, and the Putinist system is having a harder time controlling it."

The women have been held in a pre-trial detention centre since early March. Prosecutors have asked they serve a term in a labour colony.

"Whatever the verdict for Pussy Riot, we and you have already won," Tolokonnikova wrote. "Because we have learned to be angry and speak politically."