The British public wrongly believing most rapists are men ‘in a balaclava in a dark alley’ has been blamed for a slump in conviction rates for sex assaults.

The country’s top prosecutor warned that ‘out-of-date myths’ had to be tackled to persuade victims to have confidence in the criminal justice system.

New guidance will be sent to police to stress that most rapists know their victim and urge them to focus on what steps a suspect may have taken to gain consent for sex.

New guidance for police and prosecutors seeks to dispel the myth that most rapes are carried out by strangers in dark allies

The Crown Prosecution Service said its new national rape action plan will tackle the barriers that rape cases.

It has been devised by Director of Public Prosecutions (DPP) Alison Saunders and Assistant Commissioner Martin Hewitt, the national policing lead for adult sexual offences.

Mr Hewitt chaired a taskforce to investigate a fall in the number of cases of rape referred by police to the CPS and the numbers of successful rape prosecutions.

The pair called for a renewed challenge to tackle the ‘persistent myths and stereotypes’ they believe have a negative impact on cases.

In a joint statement they said that their six-month investigation had uncovered ‘pervasive myths’ about rape that exist among not only some police and prosecutors but also among society as a whole, the Independent said.

They said: ‘Despite efforts to raise awareness, many people still believe a rapist is a man in a balaclava in a dark alley, and a victim is a woman who shows her fear through fight.

‘That is very rarely the case - most rapists know their victim, many victims do not physically fight and the trauma of being raped will affect each victim differently.

‘There is an urgent need to change the discourse on rape. Our police officers, our prosecutors, our courts and our communities must reject the out-of-date myths and acknowledge the realities of rape. We also need to debate and understand the fundamental issue of consent.’

Director of Public Prosecutions Alison Saunders said the focus of cases should not be on the credibility of the victim

Last month the CPS and the Bureau of Investigative Journalism revealed that there were 2,300 rape convictions in 2013, down from 2,433 in 2010, while 129 fewer rape suspects were convicted in 2013 than in 2012.

In the last year the number of completed prosecutions and convictions has increased, the CPS said today, but the conviction rate has dropped from 63.2 per cent in 2012-13 to 60.3 per cent in 2013-14.

But new figures show an 8 per cent rise in the volume of police referrals for 2013-14, compared with 2012-13, and the CPS charged 700 more defendants over the same period, an increase of 25 per cent from the previous year.

Among the measures announced today are steps to ensure that there is better application of laws over consent, and that police and prosecutors focus on what steps a suspect may have taken to gain consent from an alleged victim.

The plan will also see the updating of the national rape protocol that is used by the police and the CPS for investigating and prosecuting rape cases.

Decisions made by police to take no further action in rape cases will be put under closer scrutiny, including monitoring of the quality of record-keeping and the authorisation of decision making, and new practical guidance will be issued to front-line police and prosecutors.

CPS rape and serious assault units will also be reviewed, as will the appointment of appropriate lawyers for rape trials, and a national conference will be convened later this year for all police and prosecutors specialising in rape cases to discuss key issues.

Ms Saunders added: ‘The new action plan makes very clear that, as with cases of child sexual abuse, the focus of any investigation and case preparation should not be on the credibility of the victim but on the credibility of the overall allegation, including the actions of the suspect.’

Professor Liz Kelly, co-chairwoman of the End Violence Against Women coalition, welcomed the rise in the number of rape defendants being charged over the last year, but said there needed to be a corresponding rise in convictions.

She said: ‘Everyone reporting sexual violence deserves the highest standards from the criminal justice system and the National Scrutiny Panel has identified actions which, if implemented consistently across England and Wales, provide an opportunity to achieve this.’

Crime Prevention Minister Norman Baker said: ‘The coalition government is taking significant action to support rape victims and bring perpetrators to justice. I welcome the work of the Crown Prosecution Service and the police to drive improvements in the response to this ugly and inexcusable crime.’

Labour’s shadow home secretary Yvette Cooper said it was ‘very disturbing’ that despite an increase in the number of rape allegations reported to the police since 2010, convictions had been falling.