Chris Evans has announced he is leaving his role as a presenter on Top Gear after one series.
He tweeted: "Stepping down from Top Gear. Gave it my best shot but sometimes that's not enough.
"I feel like my standing aside is the single best thing I can now do to help the cause.
His resignation comes after falling ratings for the show - which hit a series low on Sunday night, with an average of 1.9 million viewers.
Evans joined Top Gear after last year's departure of Jeremy Clarkson, Richard Hammond and James May.
Clarkson was fired from the show after he punched a producer following a row about the provision of food late at night while filming on location.
Evans was later signed up to front the new series alongside with former Friends actor Matt LeBlanc.
Writing on Twitter, Evans said he would continue with his other BBC commitments, including presenting the BBC Radio 2 breakfast show.
"Full steam ahead then with Radio 2, CarFest, Children In Need, 500 Words and whatever else we can dream up in the future," he said.
In a statement released via the BBC, he added: "I have never worked with a more committed and driven team than the team I have worked with over the last 12 months.
"I remain a huge fan of the show, always have been, always will be."
It is not yet clear whether the other presenters will return for the next series.
Mark Linsey, director of BBC Studios, said: "Chris is stepping down from his duties on Top Gear. He says he gave it his best shot doing everything he could to make the show a success.
"He firmly believes that the right people remain, on both the production team and presenting team, to take the show forward and make it the hit we want it to be."