Britain’s criminal justice system is “creaking” and unable to cope with the huge amounts of data being generated by technology, the head of the Crown Prosecution Service has warned in her final interview before stepping down.

Speaking exclusively to the Observer, Alison Saunders said the CPS and police were failing to investigate thousands of cases efficiently – from rape to fraud to modern slavery – and were critically short of the skills and resources required to combat crime.

Saunders, who steps down as the most senior prosecutor on Wednesday, said: “There is a huge issue to train all of [the people in] the system. In some cases, we’re seeing downloads [of online data] taking six to eight months and you have suspects and witnesses and victims waiting that long for the investigation.

Alison Saunders: ‘You wouldn’t be human if accusations didn’t affect you’ Read more

“Take one recent rape case where they met on Tinder – it took 600 police hours to go through the digital material,” she said. “You can have a judge say ‘I want a download of that iPad’ and it will take 15 officers working all weekend to get it.”

Her comments corroborate a home affairs select committee report last week which warned that police were struggling with outdated technology and at risk of becoming “irrelevant” as reported crime continues to surge, rising by 32% in three years. Saunders said: “The number of cases coming through [to the CPS] are going down, [yet] there are all sorts of things we need to work out as a system. It needs an investment of resources nationally, in capacity of forces and in future-proofing it. Who is making the plans for what is going to happen in five years’ time?”

While fraud has become the most commonly reported crime in England and Wales, with 1.7 million offences a year, only one in 200 victims ever sees the perpetrator brought to justice. Saunders admitted that many cases were simply being ignored “because it takes time and a skilled investigator”.

The capability and capacity of the police should be an urgent concern for the Home Office, she said. In their report, MPs warned of “dire consequences for public safety and criminal justice” if police funding was not prioritised.

In an emotional interview, Saunders admitted feeling bruised by her five-year tenure as director of public prosecutions, with critics branding the service “toxic” and “disastrous”. “I don’t think you’d be human if it didn’t affect you,” she said, between tears, but she felt she had “done a good job”. Saunders had to lose a third of her workforce as a result of funding cuts of more than 25%, but was proud that “morale in the service is demonstrably better” than when she arrived in 2013.

“As the DPP, I accept responsibility for what happens in the service,” she said, over the crisis in disclosure of evidence in rape cases that led to several collapsing and hundreds more being dropped earlier this year. “I could have stood there and blamed the police and say it all starts with them, but I don’t think it helps.

“We have a disclosure manual which means we are talking to the police early on about what are reasonable lines of inquiry. We give them advice that helps them.”

Saunders admitted that those initial conversations between the CPS, the police and the defence about what evidence would be used in court was “what’s been missing – that system-wide, early-doors approach to it”.

Saunders, who worked as a prosecutor within the service for 32 years and oversaw the conviction of Stephen Lawrence’s killers, will be joining the City law firm Linklaters next month.