The English National Opera confirmed they had issued staff new guidelines on using the term of endearment.

They fear use of the word "darling" could constitute sexual harassment in the workplace.

An ENO spokesman said: "Some people may have used the term 'darling' to each other for years, but there are others who may consider it inappropriate."

The policy, set out in a document called Dignity at Work, singles out the word "darling" as part of a code of conduct which addresses workplace protocol.

'Serious issues'

It tells employees: "The use of affectionate names such as 'darling' may constitute sexual harassment."

The spokeswoman added: "This isn't about banning the word, it's all about the context in which it is used.

"Whilst it may be acceptable between friends, it would be thought of very differently if the term is used by a senior colleague and accompanied by a wink.

"Our policy puts in place a mechanism which allows an employee who feels uncomfortable to enter into a grievance procedure.

"We realise that it would be almost impossible to ban the word 'darling' in theatreland, but this is about addressing some serious issues."

The policy also warns about unwelcome sexual advances and "offensive" flirtation.