(CNN) Rape laws across Europe are "dangerous and outdated," according to new analysis from human rights group Amnesty International.

The study found that out of 31 European countries, only eight -- Ireland, the UK, Belgium, Cyprus, Germany, Iceland, Luxembourg and Sweden -- have laws that define sex without consent as rape.

The overwhelming majority of countries in Europe recognize rape only when physical violence, threat or coercion is involved, Amnesty said, adding that some countries classify sex without consent as a separate, less serious offense.

In Croatia, convicted rapists can be sentenced to a maximum of 10 years, while sex without consent convictions bring a maximum of five years. In Malta, sexual offense legislation is framed in the context of "crimes affecting the good order of families."

According to a 2016 European Commission Special Eurobarometer Report on Gender-based Violence, nearly a third of all respondents (27%) said there are situations in which sex without consent is justified, including if the person is drunk or on drugs (12%), has voluntarily gone home with someone (11%), has worn revealing clothes (10%), hasn't fought back or hasn't said "no" clearly (10%).

Across the continent, weak legislation, coupled with a "dangerous culture of victim blaming," has detrimental effects for victims of sexual assault seeking to bring their cases forward, according to the group, which has called on governments across Europe to bring legislation into line with international human rights standards.

"Sex without consent is rape, full stop," Anna Błuś, Amnesty International's researcher on Western Europe and women's rights, said in a statement.

"Until governments bring their legislations in line with this simple fact, the perpetrators of rape will continue to get away with their crimes," Błuś said.

In the European Union alone, an estimated 9 million women over the age of 15 -- at least one in 20 women -- have been raped, according to 2014 European Union Agency for Fundamental Rights data analyzed by Amnesty International.

But without legal provisions to ensure a fair trial, women often choose not to report rapes.

"Women's fear of not being believed is confirmed time and time again, as we see courageous survivors who do seek justice frequently failed by outdated and harmful definitions of rape in law and treated appallingly by justice officials," Błuś said.

Although it is important for countries to include consent in their legal definition of rape, it is one of many steps they must take to protect victims of sexual violence in the legal sphere, according to Amnesty International and many women's rights campaigners.

Many countries still struggle to secure convictions, even with consent-based rape legislation.

In the UK, an estimated one in seven women has reported experiencing some form of sexual violence, placing it in the joint top five countries for the most amount of sexual assaults recorded, according to the Amnesty review.

But despite this, the number of rape convictions dropped 23% in 2017-18, compared with the previous year, according to data from the UK's Crown Prosecution Service.

"Despite the definitions of rape in the UK being compliant with international human rights standards, the Government has a duty to ensure access to justice for rape survivors is a reality," said Chiara Capraro, Amnesty International UK's women's human rights program manager, citing media reports alleging that UK prosecutors have been encouraged to "ditch weak rape cases" to improve their annual conviction figures.

The Guardian reported that the Crown Prosecution Service "denied a change of approach, and said it had a duty to ensure fairness for both complainants and suspects."

Katie Russell, a spokeswoman for Rape Crisis England and Wales, said that although she supports consent-based rape laws, they aren't enough.

"It needs to be accompanied by a wholesale understanding about what consent means," Russell said, stressing the importance of education about consent across public sectors.

"Whilst the definition is clear in our law, an understanding of that definition is completely lacking," she explained. "It's lacking amongst jurors -- and that's the general public who make up juries and ultimately decide the outcome of cases. But the suggestion is that it's also missing amongst criminal justice agents themselves. Otherwise, there's no real explanation really for why criminal justice outcomes would be backsliding whilst reporting is actually increasing."

Two high-profile rape cases this year in the UK and Ireland highlight conversations around consent and the challenges that victims of sexual assault may face in the courtroom.

In March, two former Northern Ireland rugby players were acquitted of raping a 19-year-old student at a house party in Belfast. After the trial, demonstrators protested the treatment of the woman on trial with the phrase #IBelieveHer, arguing that the defense had followed a line of inappropriate and irrelevant questioning to discredit her.

At a criminal court in Cork, Ireland, in October, the defense lawyer for a 27-year-old man accused of raping a 17-year-old asked the jurors to consider the teen's underwear as evidence of implied consent.

"Does the evidence out-rule the possibility that she was attracted to the defendant and was open to meeting someone and being with someone? You have to look at the way she was dressed. She was wearing a thong with a lace front," the lawyer said, according to the Irish Examiner.

The case prompted demonstrations across Ireland and an international social media campaign in which women posted pictures of their underwear with the hashtag #ThisIsNotConsent.

Noeline Blackwell, a human rights lawyer and chief executive of the Dublin Rape Crisis Centre, said that those trials point to a deep-rooted societal perception that the victim is partially responsible in their rape.

Blackwell agrees that consent-based laws are a crucial step in implementing wider reforms.

"It is great that at least our legal definitions are in line, but until it is properly implemented -- requiring effort and training of police, the court system and lawyers -- then we are not going to get the proper impact of the law," Blackwell said.

Jurgita Pečiūrienė, a gender-based violence expert at the European Institute for Gender Equality, said that public sentiment stresses the importance of educating the public not only on what consent means but also about the role that gender inequality plays in gender-based violence.

"In order to have effective laws and coordinated policies based on evidence, it needs to start at education," Pečiūrienė said.

"Our actions must not focus only on prosecution but on the prevention of violence in general against women, the prevention of rape and also combating the root cause of gender inequality," she said.

"We know that women often don't report rape or sexual assault because of shame, lack of support by fear of not being believed, being blamed or even experiencing more violence. But it is also part of social inequality between women and men. Consent-based laws are only one element."