Fiona Miller, above, from Middlesbrough, suffered a harassment campaign from PC Kelly Jarvis who made false statements to the NSPCC about son Tommy

Fiona Miller and her family had just finished a home-cooked roast chicken dinner when there was a knock at the door. There on the step stood a policeman, his face grave.

This was never going to be good news, anyone could see that. But no one, least of all 38-year-old mum Fiona, could have predicted what came next.

'The officer politely informed me that he was there on a welfare visit, to check on my three-year-old son,' she says.

'There had been some serious allegations of neglect, bordering on abuse.'

Anyone glancing across the kitchen where Fiona's partner, Steven, was stacking the dishwasher while their happy, healthy little boy, Tommy, played nearby that evening in January this year would have seen nothing untoward about the family, who live in a neat, semi-detached home in Ormesby, Cleveland.

Yet Fiona was terrified — so terrified, it was all she could do to stop herself grabbing Tommy and running.

Someone was out to get her, and for the first time she feared this someone might actually have the power to see the job through.

For Fiona's accuser and tormentor was a serving policewoman — PC Kelly Jarvis, a former mounted officer and riding companion of Fiona's, a woman so twisted with hatred and jealousy that she would stop at nothing to see her former friend's reputation destroyed.

'I really started to panic at that point. All sorts of horrible thoughts started going through my mind. Would I be believed over a police officer? Are they all in on this together? And most terrifying of all, was I going to lose my little boy?

'If these allegations had come from a member of the public, I wouldn't have been too concerned — but as they were from a police officer, I knew they would be taken seriously.

Kelly Jarvis and her husband Lee. Jarvis was found to have abused her powers as a police officer while with Cleveland Police, after an internal investigation

'She had power. It came with her job. In the end her lies would be found out, but how long could that take?

'Tommy might be in care for months while they investigated. The prospect of not seeing my little boy again made me more afraid than I've ever been of anything in my life.'

Fiona and Steven managed to keep their cool and eventually, satisfied that Tommy was in no immediate danger, the officer left.

In the morning, after a sleepless night, Fiona dropped Tommy off at nursery en route to her part-time job as a veterinary receptionist. Alone in the car, she broke down for the first time.

'I sat and sobbed, gagging for air and shaking. I knew there was a real risk of losing Tommy. I couldn't let that happen.'

Without another thought, she phoned Cleveland Police Station to lodge a formal complaint against PC Jarvis.

This week, Jarvis quit in disgrace, but shockingly won't face further action after an investigation by her own force unearthed a level of abuse of police powers quite Orwellian in its magnitude, and with disturbing implications for how Britain is policed today. For the PC, it emerged, was able to use her work computer to enter an 'intelligence log' on the Police National Computer against the woman she hated so much, fabricating a totally plausible and unquestioned record in her name.

Fiona with her son Tommy. The first time the family was aware of the complaints was when Tommy was three-years-old and an officer arrived at their door claiming he was on a welfare visit because allegations of neglect were made

Nothing, it appeared, was too low for her. Not only had she made false reports to the NSPCC, accusing Fiona of everything from domestic violence to leaving her son alone in the car while she went to the pub with friends — all of which was investigated and dismissed by social services — but she had also recorded 'evidence' of Fiona having had a sexual relationship with a 14-year-old boy when she was 25, a wholly malicious lie.

Fiona was only made aware of this when the disciplinary report into the PC was revealed this week.

Nevertheless, Fiona was still shocked at the level of spite: 'I was sickened, but it was all part of her vindictive campaign against me. She had told so many lies, yet still I was more worried about Tommy being put into care than anything else.'

But what could have sparked such animosity? It seems to have been nothing more than old-fashioned class jealousy.

The two women had first met in 2013 at Ormesby Grange stables, which are owned by the family of Fiona's partner, landscape gardener Steven Carter, 34, and were where Kelly Jarvis stabled her own horse.

The stables, in the picturesque grounds of a National Trust Georgian manor house, Ormesby Hall, are surrounded by hundreds of acres, all owned by the Carter family.

Perhaps it was this that piqued Kelly's envy. After all, it was a world away from the £90,000 terrace house that she and her police officer husband Lee, 41, share in Middlesbrough. She knew their modest salaries would never be able to provide such grandeur, which — as she saw it — would one day land in Fiona's lap.

'It was all about jealousy,' Fiona says. 'She would ask me lots of questions about my life and relationship. She would say: 'In a few years, when Steven's parents retire, you'll be living here in the big farmhouse.' I found her quite vulgar and intrusive, and tried not to engage with her.'

Soon afterwards, Fiona and some of her friends started to receive abusive messages on social media. She also received unpleasant text messages from unknown numbers, including a particularly disturbing one saying that Steven was cheating on her and had got another woman pregnant.

'I never believed it for a second, but of course it was really upsetting. Yet these messages came not long after Kelly started using the stables and they mirrored the way she spoke, her phrases and crudeness. I began to suspect that she was behind them, but I was determined not to let it bother me. I thought it was pathetic and sad, and just ignored her.'

Fiona, here with her son Tommy, originally met Jarvis through horse riding, but thinks jealously over the future owner of the stables is what sparked the campaign of messages

The messages continued sporadically — then, in 2015, the campaign took a sinister turn. 'A social worker turned up saying she'd received a complaint about Tommy's welfare. They had been told I was leaving him in the car on his own while I went shopping or to the pub, or that he was left wandering around the farm unsupervised.

'It was absolutely unfounded. I was asked really probing and personal questions, everything from the state of my relationship with Steven to whether Tommy was potty trained.

'It was really embarrassing, too, as they made inquiries at Tommy's nursery. I felt people would think I was a bad mother.

'It was very upsetting, but once they were satisfied there was no truth in it, I thought that was that. Back then, it didn't cross my mind that Kelly was behind these accusations, that she would stoop so low.'

By April 2015, as the abusive phone messages continued, Fiona decided she'd had enough and told Kelly to move her horse from the stables. She did so quietly, and Fiona assumed that was the end of the matter. It wasn't — not by a long way.

In January this year, Steven's parents cancelled a contract with Kelly's father, Ian Armstrong, to fit a new kitchen for them. They had employed the 63-year-old joiner without realising his relationship to Kelly until Fiona explained who he was and why it wasn't a good idea.

The next evening was the one when a police officer arrived at her door and Fiona finally put two and two together, then made a complaint against the PC.

So serious were the allegations, the case was sent to Newcastle Crown Prosecution Service. Meanwhile, an internal investigation produced a damning report into Kelly Jarvis.

It found she had exploited her training and knowledge of working in a unit which deals with malicious communication offences to harass Fiona by creating three false Facebook profiles to send her abusive and upsetting messages.

In addition, the report upheld the allegations that she had accessed police systems inappropriately and made false referrals to the NSPCC.

The nasty falsehoods went on and on, painting a picture of a filthy house full of barking dogs and of Tommy being left for hours to cry himself to sleep while Fiona and Steven screamed and shouted at each other all night — all of which were recorded as 'facts' on Fiona's police file.

In there, too, was the statement about Fiona having sex with a 14-year-old boy — a boy who is now a man. He is now in a relationship with one of her friends. When he heard of the lies being told in his name, he submitted a statement to police to deny that he and Fiona had ever had a sexual relationship.

Pulling no punches, the police report said: 'As a police officer, PC Jarvis should have been honest and diligent in the exercise of her duties and responsibilities and provided the correct details on the referral forms… she has acted in a manner which discredits the police force.'

So why did Fiona learn to her horror this week that Kelly had been allowed to simply resign and will not face further action for her reign of spiteful terror?

Cleveland Police say there are 'exceptional circumstances' for why she has been allowed to slip quietly away before a disciplinary hearing, so safeguarding her pension rights.

Fiona is understandably furious and claims she was told by police that the reason for this was cost, as it is cheaper for her just to step down than to carry on paying her while an investigation drags on.

New legislation was brought in last year to prevent police officers resigning or retiring while facing gross misconduct proceedings except in certain circumstances, which include ill health and comp-romising a covert investigation.

As to why Kelly Jarvis has been allowed to resign, a Cleveland Police spokesman said: 'In some cases officers are allowed to resign prior to a misconduct hearing where there are exceptional circumstances.' However, they would not elaborate on what these circumstances were.

Yet unthinkable as it is for a police officer to behave in this way, and as awful as the ordeal has been for Fiona, the case raises another issue — it exposes a serious flaw in the British policing system.

To judge from what occurred, there seem to be no safeguards to prevent any police officer with a grudge from doing as Kelly did: fabricating a criminal record for anyone they may happen to dislike.

David Green, who runs the Civitas think-tank, says it is very surprising that false logs can be entered on someone's record without the need for any collaboration. He also believes Kelly Jarvis should not be allowed to just go quietly.

Jarvis quit her job in disgrace but will not face further action because of 'exceptional circumstances' according to her former employer

'It's obviously quite wrong, but I'm very surprised this could have happened. You shouldn't be able to just invent a criminal record or incidents that will be on a police file.'

Civil liberties campaigner Dr Sean Gabb, of the Libertarian Alliance, described the case as 'outrageous', adding: 'The issue is that a police officer thought there was nothing wrong whatsoever in using her position to mess up someone else's life. It is blatant moral corruption and cannot be tolerated.'

Interviewed under caution, Kelly, who did not wish to comment for this story, admitted the allegations put to her and used words such as 'pathetic', 'stupid' and 'remorseful' to describe how she feels.

However, these feelings appear to have been short-lived, as this week she posted a Facebook rant standing by what she did and seeming to blame everyone, from the media to the police, for what happened.

She wrote: 'I feel very let down by my current employer however this is something I will address one day in the future.' She has also dyed her hair brown and is starting out in a new career as a horse reflexologist.

For now, Fiona is worried that after leaving the police, Kelly may feel she no longer has anything to lose and could decide to take matters into her own hands.