Rape complainants are being routinely questioned in court about their sexual histories and even the way they were dressed on the night they were attacked, according to a damning dossier of case studies to be presented to MPs this week. The findings have triggered calls for the law to be tightened to protect complainants better.

References to a person’s sexual history in court are supposed to be heavily restricted. Section 41 of the Youth Justice and Criminal Evidence Act (1999) states: “No such evidence is to be admitted, or questions allowed, unless a judge has ruled that they are admissible.”

But findings prepared by the campaign group Voice4Victims suggest many judges are allowing such questions to be discussed openly in court.

The group cites a study initiated by Dame Vera Baird QC, a former solicitor general, that found questions were raised about the prior sexual conduct of complainants in a third of the 30 rape cases attended by independent observers. In a further four of the cases, court rules stipulating the need to give the alleged victims prior notice they were to be cross-examined were ignored.

Examples highlighted by Baird’s study, which will be published later this month and is the first of its kind, include an attempt by a defence barrister to undermine a rape complainant by cross-examining her about her past behaviour, which included claims of “violence, anger, alcohol and drugs, having sex with two different men around the same time and shoplifting”.

A teenager who had a history of familial abuse, including a rape conviction against her uncle, had run away from home and was given shelter by a number of men in return for sex. The defence implied that, having consented to sex with one man, she must have consented to having sex with the defendant.

Another complainant was asked about a conviction for alcohol, her suspension from the nursing register for alcohol-related issues and adultery under a “bad character” application which is separate from Section 41. The law states such applications should not be approved if the intention is to impugn a person’s credibility.

“There is clear and overwhelming evidence that rape victims are questioned about their previous sexual history, behaviour and appearance,” said Harry Fletcher, co-director of Voice4Victims. “This would not happen to victims involved in other types of trials. Changes to legislation are needed urgently.”

Voice4Victims said it had amassed scores of similar case studies of its own. These include that of “Ivy”, who was told at a pre-trial hearing that her sexual history would not be used. However, in court she was asked by the defence how many sexual partners she had had and was accused of being promiscuous.

“M” was subjected to an attempted rape by a stranger. During cross-examination she was asked why she had chosen to wear a red dress on the day of the attack.

Plaid Cymru MP Liz Saville-Roberts will this week introduce a private member’s bill that seeks to introduce a “rape shield law”, which would prevent a defendant introducing evidence about a complainant’s past sexual behaviour. The law operates in many US states as well as in Canada and Australia.

“It is neither right nor just that a victim of rape can be questioned in court on matters not relevant to the case in hand,” Saville-Roberts said. “Yet in the recent past, victims have been humiliated by lawyers asking questions about their sexual partners, their clothing and appearance. Rape Shield Laws have been introduced in other countries to protect victims from the emotional trauma of being questioned about their sexual history on the witness stand, and it is time for victims here to be afforded the same protections.”

Last year, 35,798 complaints of rape were made to the police. But there were only 2,689 convictions, partly, campaign groups contend, because some complainants withdrew their allegations, fearing humiliation in court. The new bill also prohibits, in certain cases, the disclosure by the police of a victim’s identity to a stranger attacker.

Voice4Victims gave the example of a woman who was subjected to an attempted rape by a stranger and was then horrified to discover her identity had been shared with her attacker. The woman was contacted by half a dozen other women with similar experiences. In one example, the alleged attacker contacted his victim via Facebook.

The bill, which has drawn cross-party support, also makes provisions for safeguarding rape complainants in schools. A number of pupils who reported being raped by fellow students have been left further traumatised after their alleged attackers were allowed to return to school ahead of their trial.

Voice4Victims said Labour MP Jess Phillips had told them of three examples in her West Midlands constituency alone.