Top satellite provider says it will stop airing opposition news channel next week, in what station chiefs say is political attack

Russia's only opposition cable news channel faces the prospect of closure after the country's main satellite TV provider said it would pull the plug on broadcasts from next week.

TV Rain, one of the few surviving sources of independent news in a landscape dominated by state media, said it was now on the brink of bankruptcy. Tricolor TV announced on Monday that it was dumping the channel from 10 February.

Several other providers over the last week have also dropped the channel from their television packages. Staff say it is a political move, planned for some months and choreographed from behind the scenes by Vladimir Putin's administration.

The ostensible pretext for the decision was an online poll conducted by the channel last month. It asked whether the Soviets should have surrendered Leningrad during the second world war in order to save hundreds of thousands of lives. The poll appeared on the 70th anniversary of the siege of Leningrad, in which 800,000 people died.

The editors later removed it and issued an apology in the wake of a furious and co-ordinated attack by pro-Kremlin deputies. They have called on the general prosecutor's office to investigate the station for alleged extremism. Putin's press spokesman, Dmitry Peskov, said the channel had crossed a moral red line. Soon afterwards providers started pulling it from the air.

Tricolor's move will wipe out the channel's audience, reducing the number of Russian households that can access TV Rain from 17.4 million to as few as 500,000.

At a press conference in Moscow on Tuesday, Natalya Sindeyeva, TV Rain's general director, said the station was heavily reliant on advertising revenue for survival. This had now vanished, she said. The channel would offer its programmes to operators for free, she said, in an attempt to continue broadcasting.

The editor-in-chief, Mikhail Zygar, told agencies: "Tricolor TV is the largest operator. Its departure is a turning point. This is a red line which makes conclusively clear that a serious war is being waged against us."

Launched in 2010, TV Rain – known in Russian as Dozhd – covered the anti-government demonstrations in 2010-11, as well as the trial of two members of the punk band Pussy Riot, and the release of the jailed oligarch Mikhail Khodorkovsky. Its audience grew rapidly, especially among better-educated and middle class Russians who have been at the forefront of anti-Putin protests. Its style is lively and pugnacious.

"We were waiting for this to happen and it happened," Tonia Samsonova, London correspondent for the Echo of Moscow radio station and TV Rain, told the Guardian. She said the campaign against the channel followed a squeeze on Russia's last remaining independent media outlets, which began when Putin came to power in 2000 and had accelerated since his return to the Kremlin in 2011 for a third stint as president.

"It's impossible to be an independent, liberal, privately owned media channel in Putin's Russia," she said. "There were rumours in late December we were going to be shut down. Everybody knows that someone has put pressure on broadcasters. This is the way the Kremlin operates. Not through legislation but financial blockade."

Asked why Kremlin officials should act now, on the eve of the Sochi Olympics, a showcase event for Putin, she said: "They don't care about this. It isn't something that influences President Obama, or Merkel, or the International Olympic Committee."

Separately, the US ambassador to Moscow, Mike McFaul, announced he was quitting Russia after two turbulent years in the job. McFaul is the architect of the Obama administration's reset policy towards Russia – an attempt to improve relations following years of strain between Putin and Obama's predecessor, George W Bush.

Soon after arriving, McFaul found himself the target of Kremlin-sponsored vitriol from Russia's state media. Since 2011 under Putin, anti-Americanism has risen to spectacular levels.

The ambassador announced his departure in a blogpost on Tuesday, saying he would leave after the Sochi Winter Olympics. He explained that, having lived apart from his wife for seven months, "it is time for the family to be reunited".

He wrote: "I love my job here. It has been a tremendous honour to represent my country in Russia and I made this decision with a heavy heart. I will greatly miss interacting with my partners in the Russian government and with Russians from all sectors of society and business. I also will miss being part of a fantastic team at Embassy Moscow."

A longtime Stanford University professor, McFaul said he would be returning to California. His wife and two sons returned home last year.