Britain's Telegraph reports:

Leading dissidents from the former Soviet Union have demanded an investigation into the BBC Russian Service, which they have accused of caving in to pressure to be less critical of President Vladimir Putin's regime.

They have written to Mark Thompson, the BBC director-general, demanding an examination of what they claim is a string of examples of pro-Putin bias on the taxpayer-funded service, which has a weekly audience of two million.

The service went off air in Moscow and St Petersburg last month around the time of the murder in London of Alexander Litvinenko, a former officer in the Russian security service. "Unexplained technical difficulties" with the BBC's local partners were blamed, but there is still no service in Moscow.

The dissidents, led by Oleg Gordievsky, the former KGB spy turned MI6 agent, and Vladimir Bukovsky, an author who spent 12 years in Soviet prison camps, are particularly angered by the unexpected axing of a programme presented by Seva Novgorodsev that had run for 19 years.

Novgorodsev, who still broadcasts on the Russian Service, received the MBE from the Queen in 2004. His programme regularly had guests who were enemies of the Moscow regime, such as Litvinenko and the journalist Anna Politkovskaya whose murder he was investigating.

The BBC has also received a protest letter signed by 1,000 listeners around the world.

The dissidents' letter states: "At a time when Britain needs a strong voice in Russia more than at any point over the past decade, the taxpayer-funded BBC Russian Service radio seems to have considerably mellowed in its tone towards the Russian government.

"By design or by neglect, it has become more accommodating of Russian government views, dispensing with difficult questions and denying a platform to some critics.

"Is the BBC Russian Service trying to soften up its news coverage mindful of the Kremlin's ever-watchful eye over the airwaves? The UK taxpayer funds the BBC World Service so that Britain can have a strong voice in the world and it should not be compromised."

A BBC spokesman said: "The service remains an important and strong source of impartial and independent news and current affairs renowned for asking difficult questions on behalf of its listeners.

We reject any suggestion that we have made compromises in our questioning of any point of view in any debate."