It appeared to be an innocuous newsletter promoting upcoming musicals due to take the stage at Norwich's theatres.

But an email sent with the subject of "Something to sing along to" has sparked an apology from the Norwich Theatre group for "encouraging poor theatre etiquette".

Subscribers to the group's mailing list received the message this week promoting its upcoming musicals, including West End hits Heathers, Blood Brothers and Annie.

But after recipients raised concerns that it might encourage people to belt out the songs themselves, the company reissued the email with an apology.

Norwich Evening News: Heathers is an upcoming musical at Norwich Theatre RoyalHeathers is an upcoming musical at Norwich Theatre Royal (Image: Supplied by Norwich Theatre Royal)

It reads: "In trying to emphasise the fun and joyous nature of the musicals, we inadvertently appeared to endorse poor theatre etiquette. 

"Of course we don’t mean for people to literally sing along while they are in the theatre (just when booking their tickets or in the car on the way home!).

"We’re really sorry for any misunderstanding, upset and the careless language."

It comes at a time of heated debate among theatregoers about the appropriateness - or otherwise - of live audiences singing along to musicals.

Police had to be called to a performance of The Bodyguard in Manchester last month after a row about members of the audience singing and dancing along to the music.

The show had to be stopped 10 minutes before the end and two women were removed from the theatre.

The incident triggered a national debate over the way to behave at the theatre.

ITV's This Morning prompted scores of complaints to Ofcom after presenter Alison Hammond said she was "devastated" to hear the women had been ejected.

Following the complaints, she withdrew her comments.

Norwich Evening News: Alison Hammond is to take part in Strictly Come Dancing

"I am a great supporter of theatre and the arts and would never sing at the top of my lungs at any performance," she said.

Theatre veteran Ben Elton also waded into the debate, saying audiences should "apply good taste and good manners".

Norwich Evening News: Ben Elton who is returning to stand-up comedy. Photo: PA/Dominic Lipinski

Mr Elton, the writer of Queen musical We Will Rock You, told BBC Breakfast: "Of course, nobody’s paid to sit next to somebody [singing]."

A Norwich Theatre spokeswoman said: "After the situation with an audience member singing during the Bodyguard in Manchester and it being something of real sensitivity with performers, we would never want to encourage this.

"It was pointed out by a handful of people that a clumsy email subject line suggested we were.

"So we wanted to correct, that’s all."