In a further example, victims of alleged assaults will be told if the defendant claims the crime was self-defence.

Miss Saunders admitted the guidelines would be controversial but insisted they were “within the parameters of a fair trial”.

The guidelines follow a number of high-profile cases in which witnesses or alleged victims have suffered during or after the trial process, including violinist Frances Andrade, who was found dead from an overdose a week after giving evidence against her abuser in January 2013.

Mrs Andrade, 48, told the court during her cross-examination: “This feels like rape all over again.”

A coroner later said he could not be sure Mrs Andrade committed suicide and recorded a narrative verdict.

In another case Nigella Lawson, the cook, described her experience as a witness in the 2013 trial of her ex-husband Charles Saatchi's personal assistants as "mortifying" and said she had been "maliciously vilified without the right to respond".

Miss Saunders said: “This aims to give prosecutors the confidence to engage with victims and witnesses without fear of any allegations of ‘coaching’ or going too far.

“It’s about telling them what the defence case is likely to be in general terms. But it is not about telling them what their evidence should be.”

Miss Saunders said the guidance was likely to play an important role in rape and other sex cases but also in assault or harassment prosecutions.

The DPP insisted the new measures would not add extra time to court cases and that it would not involve any additional costs.

“Some people may think it’s beginning to go too far, talking to victims and telling them what the general defences will be and warning them about what will happen within court,” the DPP said.

“Some [lawyers] who always defend may think it’s pushing it. The criminal defence Bar may well have anxieties about it.

“But I think this is within the existing boundaries and does not contradict anything about coaching or rehearsing victims and witnesses.

“It’s about getting them to give their best evidence within the parameters of a fair trial.

“We have not had guidance like this before and I think it’s long overdue.”

The CPS guidelines also say prosecutors should:

• Advise victims and witnesses that giving evidence is not a “memory game” and inability to answer a question should not be seen as a sign of weakness.

• Ensure they do not engage in “thoughtless interaction” in and around court where they might be overheard by victims or witnesses.

• Make a special effort to thank victims and witnesses after they have given evidence.

Tony Cross QC, chairman of the Criminal Bar Association, said: “The general idea is very laudable but defence and prosecution barristers will find many of the proposals dangerous and impractical.

“There are real evidential concerns, including a risk of rehearsing witnesses.

“Our system of justice demands that the first time a witness hears the detail of the defence case is when it is put to them in court, so the jury see their reaction.”

Mr Cross said it would create a vast amount of work for “over-pressed” CPS lawyers.

Conversations with victims and witnesses which take place under the guidelines would have to be scrupulously recorded to avoid the danger of disputes in court, he added.

“If a witness disagrees with what has been recorded by the lawyer then that barrister could become a witness in the trial he or she is supposed to be prosecuting, meaning they would have to withdraw and the whole trial would have to start again,” Mr Cross said.

Jeremy Wright, the Attorney General, welcomed the draft guidelines, which are open for an eight week consultation.

“I am very pleased this guidance is subject to an open consultation to the public,” he said.

“The DPP has already written to me to ask for my feedback and I’ll be providing her with my thoughts.

“I encourage the public, especially those who have been through the experience of being in court as a witness, to share their views and help make the system better.”

(The Telegraph)