By Sebastian Usher
BBC world media correspondent
Romanova said she could not perform her duties "honourably"
Concern over the lack of independence in Russia's media has been intensified by the resignation of two senior TV journalists.
Their TV station was until recently one of the last voices still refusing to toe the Kremlin's line.
Olga Romanova, a star presenter at Ren TV, and her editor Yelena Federova said they were resigning because they could no longer perform their professional duties.
Two weeks ago, Ms Romanova - the presenter of "24", the flagship news programme on Ren TV - was prevented from going on air on the orders of the head of the station.
Several items critical of the government were dropped from the programme.
Ren TV tried to play down the affair, saying it wanted to try out new presenters.
But Ms Romanova said the move was politically motivated and that she had been taken off air for accusing the station's management of blocking stories critical of officials.
She and her editor have now handed in their resignations.
Ms Romanova told the radio station Ekho Moskvy why she was leaving.
She said her "team" had "tendered their resignations because the situation of the channel makes it hard to stay human, let alone perform one's professional duties".
Ren TV was started by an independent mother and son team, Irena and Dmitry Lesnevsky. But they sold their remaining stake earlier this year.
The channel's ownership is now split between the Russian steel group Severstal, the natural resources company Surgutneftegaz and the European media giant RTL.
The head of Severstal, Alexei Mordashov, is close to President Vladimir Putin.
There were warnings that the station's independent line would be lost under its new ownership.
These fears appear increasingly to have been fulfilled.
With the next presidential election due in 2008, all Russia's TV stations are now directly or indirectly under the Kremlin's control.
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