Sheridan Smith has pulled out of her leading role in West End show Funny Girl for up to four weeks because of "stress and exhaustion".
Understudy Natasha Barnes will replace the 34-year-old Cilla star.
Barnes has stood in for the last three performances that Smith has missed this week, including one on Wednesday night.
In a statement posted via a tweet, the producers of the show said: "Sheridan Smith will be taking a leave of absence from Funny Girl due to stress and exhaustion.
"The entire team at Funny Girl is thinking of Sheridan, and know she is getting the rest and support she needs during this difficult and stressful time."
The statement continued: "We will all miss her enormously and send her our love and best wishes - and we are looking forward to her return to the show in due course."
Smith first missed a performance on Monday, the night after the Baftas TV ceremony.
She had hit out at suggestions in the media that she had not taken well her failure to secure the Best Actress award.
Suranne Jones took home the Bafta for Doctor Foster, while Smith had been nominated for her role as the late cancer blogger Lisa Lynch in The C Word.
On Twitter, she accused the press of "bullying" and was supported by her fans.
She tweeted: "When will u stop bullying? I had the best night in memory of my girl @LisaLynch."
The Mrs Biggs star tweeted an apparent reference to her absence on Monday: "Well done press! U let down me,the cast & everyone who spent money to see me. I apologise. Profusely!"
The tweet continued: "Sorry! Sorry I'm not strong enough."
The Savoy theatre said Smith was "indisposed".
On Tuesday, it was announced that Barnes would play Fanny Brice due to Smith's "indisposition". The theatre repeated the same announcement on Wednesday afternoon.
Smith has not tweeted since May 10 when she said apologised again to her fans.
"I love you who have my back, beyond belief. Sorry x."
The opening monologue of Baftas host Graham Norton appeared to contain a joke at Smith's expense.
He quipped: "We're all excited for a couple of drinks tonight. Or, as it's known in theatrical circles, a few glasses of 'technical difficulties'."
It came less than two weeks after a performance of Funny Girl was cancelled halfway through, which producers said was down to "technical difficulties".
Smith had earlier denied speculative reports in the press that the show had to be stopped early because she had been drinking.
A spokesman for Smith has said the allegations were "categorically not true".
Funny Girl is showing at the Savoy until October 8.