The number of rape convictions has fallen to a record low in England and Wales after plummeting by a quarter in a year, new figures show.

Just 1,439 alleged rapists were convicted of rape or lesser offences in 2019/20 – down 25% from 1,925 the previous year, according to data released by the Crown Prosecution Service (CPS) on Thursday.

The number of completed prosecutions also reached a record low, with 2,102 in 2019/20, compared to 3,034 in 2018/19, a fall of around 31%.

Victims’ Commissioner Dame Vera Baird QC branded the figures “utterly shameful” while women’s groups said it shows the “effective decriminalisation of rape”.

Police chiefs said it is getting harder to achieve the standard of evidence needed to charge a suspect and bring the case to court.

The CPS said it was “working hard to reverse the trend we’ve seen in recent years” as a new five-year strategy was unveiled to improve the rate of conviction in rape cases.

Director of Public Prosecutions Max Hill QC told the BBC Radio 4 Today programme: “I do accept the scale of the problem but we must also accept if we are talking about that, that looking back three or four years some serious mistakes were also being made.

“There were cases going to court which shouldn’t have been going to court, so we have had to eradicate that as well.”

The CPS figures also show a drop in the number of rape cases referred to the CPS by police, with 2,747 in 2019/20, down from 3,375 the previous year – around a 19% decrease.

And the average time for the police and CPS to bring a charge increased to 145 days, compared with 108 in 2018/19.

The National Police Chiefs’ Council (NPCC) described the fall in the number of convictions as “very concerning for us”.

A joint statement from the NPCC’s leads for rape, domestic abuse and charging said there are a number of reasons for the drop in referrals, many due to the way forces work, but that police have been working with the CPS to “streamline” the process.

“However, we are hearing from our officers that it is becoming harder to achieve the standard of evidence required to charge a suspect and get a case into court,” a statement said.

“Victims tell us clearly how important it is to them to have the evidence tested in this way.

“Investigators are working incredibly hard to try and reach that standard, but in some occasions when they are unable to do so they are taking local decisions through gatekeepers and supervisors.

“We are also concerned about the increasing length of time it is taking to reach the point of charge. Many issues are contributing to this including more cases, more material and evidence to gather and the high evidential threshold we need to meet.”

The CPS strategy, published on Thursday, includes a joint action plan with police and giving officers legal advice early in investigations.

Mr Hill also said more alleged rape victims should be allowed to pre-record evidence to avoid coming to court for trial, and victims who do need to attend should be offered a “digital walkthrough” of the process so that they know what to expect.

He said “trends are moving in the right direction”, pointing to a rise in the proportion of cases referred to the CPS by police that result in charges.

“I’m very anxious to ensure that everyone understands that the Crown Prosecution Service, just like our partners in the police and everybody else involved in dealing with these truly awful crimes, is keen to do more, to look further and to work harder to improve in the interests of the whole system,” he said.

“What I’m saying today in launching our rape and sexual offences strategy for five years through to 2025 is that the CPS will continue to develop, to train our people and to work out how to help individuals and their cases to come through the criminal justice system.

“We need to continue to achieve a balance between the needs and the rights of victims and those of suspects, but if we work harder we will see continuing improvement.”

But Dame Vera, the Victims’ Commissioner for England and Wales, said: “These rape statistics are utterly shameful with 1,500 fewer rapists being convicted than three years ago. Rape is a serial offence and rapists carry on until they are stopped.”

Earlier this month, a report from Dame Vera warned that the country is in effect witnessing “the decriminalisation of rape” and women’s groups said the latest figures show this is continuing.

End Violence Against Women (EVAW) director Sarah Green said: “We have seen a vacuum of leadership and accountability within the CPS when it comes to rape, with no recognition of the harm done to the thousands of survivors being failed by the system.”

The group was on Thursday given the green light to pursue a legal challenge against the CPS over the decline in rape prosecutions, with a judicial review case set to be heard by the Court of Appeal.

EVAW says since late 2016 the CPS has taken a series of actions which have changed the way alleged rape cases are considered by prosecutors when they are deciding whether to bring charges against someone.

The CPS is opposing the legal challenge, arguing there has been no shift in policy and has previously said the claim is “beyond the bounds” of a judicial review of policy.

According to a report from the Police Foundation published on Wednesday, the number of rapes reported to police rose by 260% between 2013 and 2019.

But data from the Home Office showed that in the 12 months to March just 1.4% of 55,130 offences recorded by police led to prosecution. Of the cases that were closed, 41% collapsed because the victim did not support further action.