As the director of public prosecutions, Keir Starmer is responsible for prosecutions, legal issues and criminal justice policy. Since he took up the post in November 2008, he has had to contend with the case of the death of Ian Tomlinson at the 2009 G20 Summit, the controversy around assisted suicide and has been drawn into the News of the World phone hacking scandal. Now he faces another challenge.

Last autumn, a 28-year-old mother began an eight-month prison sentence for "falsely retracting" a rape allegation against her husband, despite the court accepting that she had suffered prolonged domestic abuse and had withdrawn the rape accusation under pressure from her husband.

News of the case triggered outrage, and the woman was later freed by the court of appeal, with the lord chief justice, Lord Judge, commenting that there should be a "broad measure of compassion for women who had already been victimised".

To avoid the possibility of any repetition, Starmer, has since December requested that all perverting the course of justice cases that involve retracted rape and domestic violence allegations should be submitted to him for approval.

The nature of rape as a crime that usually occurs in private, with only the victim as a witness, makes it challenging to prosecute. How to handle allegations of rape that are subsequently retracted by the victim is an equally fraught part of law. When is it in the public interest to prosecute the woman for perverting the course of justice?

Recognising that mistakes have been made, Starmer has drawn up interim guidance, published in February, to help prosecutors establish where the public interest lies in this delicate area. Over the past month, he has had two detailed consultation sessions with around 20 domestic violence and rape support groups, to be sure that their concerns are reflected in the guidelines, and the public has until 6 May to register its thoughts on the Crown Prosecution Service (CPS) website.

His main objective, he says, is to ensure that victims have sufficient confidence in the system to report the crime. "Confidence is really important here: general public confidence but, more importantly, confidence among victims to come forward," he says. "We prosecute about 4,000 rape cases a year, and most of the time it is done really well. But when things go wrong it attracts a lot of publicity."

Malicious

Since he began reviewing files of evidence, he has seen 24 new cases involving charges of perverting the course of justice in relation to retractions of domestic violence and rape allegations. He and his staff have to establish whether the original accusation has been retracted because it was malicious, or because the woman who made the accusation has come under pressure from a violent, abusive partner.

If there is evidence to suggest that the woman has withdrawn an allegation concerning a rape or an act of domestic violence that actually happened, then the new guidance makes it clear that no case for perverting the course of justice should be brought. It states: "The prosecutor should be aware that victims of domestic violence may sometimes retract a true allegation: for example as a result of pressure, fear of violence, or intimidation, or because of other factors such as a desire to give the relationship another chance."

It adds that anyone who deliberately makes a false allegation may be guilty of perverting the course of justice, but clarifies (crucially) that "the prosecution must prove that the allegation was in fact false. If there is any question as to whether the original allegation might in fact have been true, then there is not a realistic prospect of conviction, and no charge of perverting the course of justice should be brought."

"We tried as a policy to draw a line between malicious falsehood cases on the one hand and on the other cases where it may be that the allegation is true," Starmer says. "Unless you can prove, to criminal standards, that the allegation is false, then we are not going to be taking a case for perverting the course of justice."

To do that, prosecutors will be encouraged to study medical evidence, listen to the 999 call recording, and examine CCTV footage. "Underlying all this, we want to give complainants the confidence to come forward in the knowledge that only if it is a deliberate lie are you likely to face perverting the course of justice charges. You're not going to be facing them because you weren't supported or because you retracted under pressure for other reasons," he says.

"If people fear that if they don't see it all the way through, they might be prosecuted, then that is not helpful, and that is critically what we need to address."

The guidance will not make the law more lenient towards those who make up allegations of rape. "Where there is a deliberate falsehood, where someone is falsely, and wrongly accused of rape, and it is baseless, then we will prosecute. Particularly where they [the accused] have been arrested, charged and tried," he says.

But even here the guidance is nuanced. One case, where the allegation was retracted, and later turned out to be false, involved a girl and a boy aged 14, he says. "So you have this really tricky situation. For a 14-year-old boy to be accused of rape, and for everyone to know about it, it is pretty awful for him and his family. But she was of a similar age. We didn't prosecute; there was enough evidence, but the question was whether a prosecution was in the public interest," he says.

The guidance offers help on what factors might reduce the public interest in prosecuting – taking into account, for example, whether the "suspect appears not fully to have understood the seriousness of making a false allegations (bearing in mind his or her age and maturity)".

Starmer is also focusing on the way the CPS handles domestic violence generally. Last week, the Home Office announced automatic multi-agency reviews for every death as a result of domestic abuse in order to try to learn the lessons from it, and Starmer promised more support for victims. "A million women experience domestic violence year on year; we are still seeing two women killed every week by their partners; women are 54% more at risk of sexual violence from their partners than from anyone else; women are more at risk from violent crime in their own home, than anywhere else. So it needs to remain a priority for us," he says.

Cuts

The CPS is facing a 25% cut over four years, and Starmer says these cuts are forcing him to focus attention on deciding what should be the service's key priorities. "The spending review last year was one of the toughest this organisation has had to endure. We are restructuring and trying to make our team more resilient, but I thought we needed to think to be clear what our priorities were," he says. "I'm determined that the budget cuts will not affect our service to victims of sexual offences and domestic abuse."

Neither he nor his colleagues will spell out which areas are becoming less of a priority as a result; Starmer's message seems to be that whatever does lose out as a result of financial pressures, it won't be this area. Behind his determination, lies a sense that success rates are still not good enough.

But he stresses that the system is improving. "Ten years ago we were still in the era of saying, 'It's just a domestic.' Now, there are many more cases of domestic violence brought than even five years ago. The change in mindset came when we said to prosecutors: 'When you are building the case, assume from the outset that you might end up with a woman who won't support the prosecution.'"

Now prosecutors are guided to get photographs or videos of the scene, and secure the 999 recording. "It really does make a difference. The conviction rate used to be only 49% – only one out of two cases. Now it is up at 72%," he says. "The 999 tape is critical, once that's served, the likelihood of a guilty plea goes up dramatically. Very often, you hear a very distressed woman in the background. The defence that nothing happened is just impossible. "