Moscow, Russia - In an unusual move, a senior Russian official has joined academics in criticising what he described as "the creeping clericalisation" of Russia.
Vyacheslav Glazychev accused the Russian Orthodox Church of interfering in the affairs of state.
His criticism came after 10 academics, including three Nobel Prize winners, asked President Vladimir Putin to stop the Church "destroying science".
Organised religion has grown hugely in popularity in post-Soviet Russia.
'Imposing ideology'
Vyacheslav Glazychev, a senior official in the Public Chamber, an advisory body charged with scrutinising parliament, said he wanted to defend the values of a normal, tolerant and secular society.
He accused the Church of undermining secularism.
He said attempts by the Orthodox Church to have religious studies introduced in schools were an attack on the state itself.
Anyone challenging the Church, he alleged, faced being ostracised.
Russia's leading human rights activist, Lev Ponomaryov, agreed.
He said the Church was trying to claim the right to impose a state ideology.
Earlier, leading academics published an open letter addressed to Vladimir Putin, calling on him to ensure the state remained secular.
New tolerance
The reaction from Russia's major religions was strong.
A spokesman for the Orthodox Moscow Patriarchate said the criticism consisted of "unsubstantiated, Soviet-style accusations".
The head of Russia's Jewish Congress said it was the Church's "holy duty" to speak out on key matters of state and nation.
However, the head of Russia's Muslims disagreed.
Attempts to enforce religious education in schools, or introduce priests into the army, were a violation of the Russian constitution, he said.
Post-Soviet Russia has seen a phenomenal growth in religious belief after decades of official atheism and religious persecution.
Only religions considered traditional - Orthodoxy, Judaism, Buddhism and Islam - are allowed.
The Orthodox Church, in particular, has been outspoken in its support for Vladimir Putin and his overarching idea of reviving Russia's greatness.