One moment, you’re a high-flying economist and cabinet minister’s wife, the next a cause celebre – the scorned spouse in the dock for lying about your husband’s speeding offence, then vengefully leaking it to the press.

Then with the nation’s press snapping your every move, you are convicted of perverting the course of justice and incarcerated in Holloway with drug addicts and thieves. How do you survive and cope with the notoriety?

Vicky Pryce credits her nine-week jail stay with opening her eyes, and changing her outlook.

“You change your priorities about what matters and doesn’t matter. You realise how easy it is to go from being normal to being an offender,” says the mother-of-five, whose former husband Chris Huhne was also convicted.

“I remember writing to all the children saying, ‘Don’t leave the house while I am away in case something happens’.

“If it happened to me, it can happen to anyone. That changes the way you look at people and judge them.”

Since leaving prison last May, the 61-year-old has been determined to “give something back”.

Not only has she taken a senior (unpaid) Civil Service job advising Vince Cable, as well as “normal economics work”, she’s written a book Prisonomics – part memoir, part pin-sharp dissection of our flawed criminal justice system.

All proceeds go to Working Chance, a charity helping women former offenders find employment.

Pryce is full of energy and purpose – reeling off facts about the raw deal for women in prison, from their likelihood of reoffending to the terrible emotional cost for their children.

It costs £56,000 a year to keep a woman inside, 80 per cent are on short sentences of less than 12 months, 53 per cent have been sexually, emotionally or physically abused as children, more than half have suffered domestic violence, 37 per cent have contemplated suicide, a third have attempted self-harm and 40 per cent lose their homes while in prison.

Touring the country

She is touring the country from book festivals to law faculties in hope of raising the debate. “My experience has been quite useful – the book is encouraging a lot of debate and I am very happy with that. That’s why I wrote it,” says Pryce, who admits the sensational nature of her case made it hard to slip back into normal life.

“It’s very difficult for someone like me to forget about it. I am well known. Everything I do gets followed. Living quietly wasn’t an option, so I might as well do something good with it. I am happy to help and talk on the difficult questions. That’s my way of giving something back.”

Clearly anxious not to make things personal, she talks passionately about the general welfare of women prisoners.

“These women are a socially disadvantaged group. A large percentage have drug and alcohol addictions, mental health problems and poor education. The system has failed them already. They are basically victims for a large part of their lives and become offenders because they have been victims.

“Many have depression, dependency and self-esteem issues and have done something for or with husbands boyfriends, brothers and fathers.

“They’re in for trivial things – shoplifting, passing stolen goods to feed other’s drug habits or their own.

“There’s also a double whammy that men misbehaving is treated as the norm, while if you are a woman, you are not meant to do anything wrong. The press goes to town – it even makes it into judges’ summations.”

Cost to society

As a government economics adviser, she’s well placed to break down the cost-benefit of the criminal justice system and her expert opinion is that prison doesn’t add up. “The cost to society is enormous. It makes no sense because it doesn’t help anybody.

“When women emerge from prison, only 8 per cent go into full employment. They are seriously disadvantaged because they have children. A third are lone mothers – when a child’s mother goes into prison, only 5 per cent stay in their house. It’s very destabilising. Many end up in care and that disruption makes them significantly more likely to demonstrate anti-social behaviour or end up as NEETs [people not in education, employment, or training].”

Without rehabilitiation or training while inside, Pryce says the women emerge a further burden on the state.

“Having access to parenting skills, programmes to raise self-esteem or other support would be much more effective.

“The system is not fit for purpose. Sending people to prison doesn’t act as a deterrent to crime – many reoffend within a year.”

Despite being close to government and politics for years, Pryce is no cynic. Rather she’s earnestly optimistic that, if people are presented with the facts, they will accept rational arguments.

“Society is quite willing to think of people differently if things are explained to them. The raw facts need to be presented. I think people want to think more deeply about it.”

She adds: “The issue is political. Politicians want to be seen to be tough, but crime is coming down and everyone accepts it’s nothing to do with putting people in prison. More people are there because we have made more offences carry custodial sentences. I don’t necessarily blame the judges – people end up in prison because there is no alternative.”

Pryce, who calls for more community orders and custody nearer home so women can stay in touch with their children, says her own experience was far from the stereotype of bitching and bullying, She found empathy and kindness – fellow cons brought her extra blankets and a TV –and a “pretty humane” bureaucracy.

“I didn’t know what to expect about prison. I didn’t know anyone who had been. I was struck by the solidarity, not only to me because I was someone who everyone knew, but they were really supportive of each other, which made it more bearable. Prison exceeded whatever expectations I may have had. I was dealt with with reasonable dignity.”

The hardest thing she found was “loss of control”, “loss of liberty” and constant separation from her family.

“You try to have as much control over what you do, but it’s limited by how you have to behave. Knowing your family are there is hugely important.”

During the highly publicised trial, she kept withdrawing sums of cash, anxious to leave her children with enough money until her release.

This led to the bizarrely humorous situation of unloading £1,490 in notes and coins from her handbag at Holloway’s reception.

“I had assumed the worst but didn’t know how long I would be inside,” she explains. “I thought I was on top of it but I clearly wasn’t. This money in my bag that I didn’t remember caused huge hilarity and eased the atmosphere.

“Walking into the unknown, in my life I had stayed in many horrid places around the world, in dreadful hotels and scary environments. I thought, it can’t be worse than that. I will survive this too. I am quite an easy person and can get by with very little.”

Pryce’s book argues that custodial sentences are often excessive for non-violent crimes carried out by women, and critics have observed that she has yet to say sorry for what she did – does she consider her own sentence unfair?

“I tried very hard not to make this a personal issue. Other people might say that, but it would be completely wrong if I turned this into a private thing. My view was I would accept the judgment whatever the jury decided and just get on with it. No point thinking what could have happened.”

Vicky Pryce is in conversation with Peter Stanford at the London Jewish Cultural Centre, Ivy House, North End Road, on May 19. www.ljcc.org.uk, 020 8457 5000.