A trainee barrister has been jailed after being found guilty of falsely accusing her former boyfriend of a series of rapes and assaults.

Sentencing Rhiannon Brooker, 30, to three and half years, the judge Julian Lambert said she had acted in an "utterly wicked" way and argued that false claims made it more difficult for real rape victims to be believed in court.

There was anger from women's rights campaigners who claimed that such severe sentences would put off rape victims from going to the police for fear they could face prosecution if allegations were not proven. There were cries of "Shame" and "Miscarriage of justice" as Brooker's sentence was handed down.

Brooker's former partner Paul Fensome, a railway signalman, was held behind bars for 37 days after she accused him of a string of rapes and assaults. While in custody, Fensome was held in a secure wing after rumours went around that he was a paedophile. He has since received £38,000 compensation.

Alibis, evidence from Fensome's phone and his work shift patterns undermined Brooker's accounts. Injuries were judged to have been self-inflicted and the police dropped their investigations into Fensome and turned their attention on Brooker.

Brooker initially told police she had made false accusations. But when she was charged with perverting the course of justice she retracted her confession. She was found guilty of 12 offences relating to false allegations of five rapes, six assaults and one false imprisonment.

Mitigating, Sarah Elliott QC said Brooker's motive had not been financial, she was not attention-seeking and she had not acted out of malice. Elliott dismissed a claim by the prosecution that she had lied to cover up for poor performance in her barrister training, pointing out she was in the top 10% of students.

Elliott said Brooker was a vulnerable woman who had a "damaged upbringing", but the birth of her daughter with a new partner nine months ago had "profoundly changed her". She added: "Every single day in prison will be agony."

The judge said Brooker's "relentless" lies had created a "detailed web of falsehood". He said false allegations could have an "insidious effect" on the public, causing scepticism and making it harder for real victims to be believed.

The support and campaign group Women Against Rape (WAR) was among more than a dozen organisations and lawyers who wrote to the judge arguing that a harsh sentence would put women off coming forward to report rapes for fear they would not be believed.

They wrote: "The prosecution was not in the public interest. A prison sentence will put even more women off reporting, enabling even more attacks from violent men. The resources spent on prosecuting Ms Brooker should have been put into prosecuting rapists and other violent men."

A note seen by the Guardian made by an Avon and Somerset detective about the case suggests there was concern in the force about a "reputational risk" over any move to drop of the case against Fensome. The force rejects claims by WAR that it prosecuted Brooker to cover its back.

A force spokesperson said: "The decision to charge Rhiannon Brooker with perverting the course of justice offences was not only due to the strength of the evidence but also because it was in the public interest to do so. There are many serious aggravating features in this case. False claims have a clear adverse impact on victims reporting incidents to police and the prosecution of genuine cases."

Ch Supt Sarah Crew, force lead for rape and sexual offences at Avon and Somerset police, said: "It would be a travesty if this case were to undermine the confidence and experiences of victims. We want to assure all victims of rape, sexual assault and domestic abuse that we will listen to and support you every step of the way."

James Ward, crown advocate for the Crown Prosecution Service, said: "This case was brought both to protect the integrity of genuine rape allegations and victims of rape and because of the devastating effects false allegations of sexual offending can have on genuine victims, innocent people so accused and their families."