Russian plans to mark 60 years since the end of World War II will make a mockery of the occasion, world leaders have been warned.
Mr Putin is accused of betraying the ideals that won World War II
A group of politicians, academics and human rights campaigners have signed an open letter attacking Russia's record on democracy and political freedom.
They say official ceremonies to be held in Moscow undermine the memory of those who fought and died in the war.
Signatories include ex-Czech President Vaclav Havel and former US ambassadors.
Moscow has also upset neighbours Georgia, Estonia and Lithuania, who all plan to boycott Monday's ceremonies.
Georgian President Mikhail Saakashvili is staying away because Russia and Georgia have failed to agree on a timetable for closing Soviet-era bases in his country.
In a separate row, Estonia and Lithuania are boycotting the ceremonies because they say their liberation from the Nazis marked the start of Soviet occupation.
Latvia will send dignitaries - but along with Estonia and Lithuania it wants Russia to apologise for the Baltic states' annexation by the Soviet Union in 1940.
Russia sees itself as the main power which helped bring freedom to Europe, defeating the Nazis at an enormous human cost - 30m Soviet lives were lost.
Russian President Vladimir Putin said recently that the three Baltic states had been "treated as pawns in world politics" but said Moscow had already apologised and would not do so again.
"Must we do this every day, every year? That is downright senseless," he told German television.
Pro-democracy campaigners in Europe and the US have expressed growing concerns about modern Russia.
During wartime Allied leaders fought together against Germany
In the letter, to be published in full in the UK's Financial Times newspaper to coincide with the 9 May ceremonies, signatories accuse Russia of betraying the principles behind victory in 1945.
They write: "[We] believe the venue and hosting of this event are altogether unsuited to the fundamental principles for which that historic victory... was achieved."
Russia in 2005 lacks strong democratic institutions, while political freedoms, civil liberties and the rule of law are weak, the signatories allege.
"It seems to us a mockery of the occasion to gather there in honour of the 20th century's climactic sacrifice for Europe's freedom."
As well as Mr Havel, the letter's 75 signatories include former prime ministers of Estonia and Bulgaria and academics and democracy activists from eastern and western Europe and the US.
Several current and former members of the European parliament, US congress and UK parliament also signed the letter.
Richard Allen, former national security adviser to former US President Ronald Reagan, has signed, alongside several former ambassadors.
Russia has been accused of concentrating too much power in the hands of the Kremlin, and US Secretary of State Condoleezza Rice recently criticised levels of media freedom.