EastEnders executive producer Louise Berridge has quit the BBC One soap after two years in the role.
Louise Berridge will work on a "major new drama project"
She left after ratings fell from an average of 13 million at the start of the year to 11 million in June.
"I've loved every minute of my time on EastEnders, but felt it the right time to move on to new challenges," Ms Berridge said.
She will be replaced by Kathleen Hutchison, currently executive producer of BBC One hospital series Holby City.
"It's been a privilege to lead BBC One's number one show through the last two years, even when faced with the unexpected," Ms Berridge said.
"We now have some very exciting plans in place with forthcoming storylines, of which I'm very proud.
"I'll miss working with all the crew and cast, but I know EastEnders will be in good hands, and continue to go from strength to strength."
In July Ms Berridge defended the soap after a Mirror newspaper survey found that 57% of viewers thought it had lost its appeal.
However, she admitted that some storylines featuring the show's Ferreira family were "not our finest hour".
Mal Young, the BBC's controller of continuing drama series, said Ms Berridge had done a "superb job" as executive producer.
"It's a relentless job, both as manager and lead creative of over 200 hours of primetime drama, in a very public spotlight," he said.
"There are not many people talented or resilient enough to handle this job, and Louise has proved herself one of the few. Without Louise, there'd be no Alfie Moon, no Dennis Rickman."
He said Ms Berridge would now work on a "major new drama project" for the BBC.
Her successor, Ms Hutchison, said: "This is my dream job. Soap reaches the hearts of the nation with iconic characters and stories. I can't wait to get stuck in and create a few more on EastEnders."