Men who have sex with drunken women face a higher risk of being convicted for rape even if the alleged victim appears to give her consent, under reforms suggested by the government.

A new white paper is expected to propose that judges should give far firmer guidance to juries in cases where there is a question over whether a woman claiming she was raped was capable of giving or withholding consent to sex.

If she was deemed so drunk she was incapable, the man would be far more likely to be convicted of rape.

The change would mark a significant departure from the current law, under which a man can escape conviction if he can convince the jury he believed a woman wanted sex, even if she was drunk.

The new law places a heavy responsibility on men to be certain women are sober enough to know what they are doing.

The white paper, which has been signed off by ministers and is expected to be published this week, follows months of discussions involving the Home Office, the Ministry of Justice, police and women’s support groups about how to raise the conviction rates for rape.

Police recorded 14,449 allegations of rape in 2005, one of the highest figures ever. However, only a fraction of rape cases ever reach court – about 12% – and few of those which do result in convictions.

The white paper will leave far more discretion to judges and juries than would have been the case under an earlier proposal to have legally determined thresholds of alcohol consumption above which a woman would be deemed incapable.

The government’s decision will disappoint those demanding more hard and fast rules to ensure more convictions. But the final version of the white paper follows a pivotal ruling by appeal court judges earlier this year.

They declared it would be “unrealistic” to create a “grid system” on alcohol consumption in rape cases, because people’s ability to cope with drink varies so greatly.

Ministers describe the appeal court decision in March as “incredibly useful” because it set a legal precedent. They say it has exposed the need for more help for juries considering such cases.

Benjamin Bree, a 25-year-old software engineer, was initially sentenced to five years in jail for raping a 19-year-old student in her halls of residence at Bournemouth University after she convinced a jury she was too drunk to consent to sex.

But the deputy lord chief justice, Sir Igor Judge, sitting with Lady Justice Hallett and Mrs Justice Gloster, overturned the conviction, arguing the jury had not been given clear enough directions.

They ruled that capacity to consent “could evaporate” well before someone became unconscious, but whether this was so “depended on the actual state of mind of the individuals involved on the particular occasion”.

A minister involved in the proposed rape law reforms said: “On cool reflection, it is clear we cannot have some sort of hard and fast law about how much drink is too much drink. What we need to do is provide better training for judges and juries on how to decide whether a woman was capable of consent.”

Other proposals in the white paper include the introduction of a “victim’s advocate”, who is not a lawyer, to give practical support to rape victims through bringing their cases to court and to help them see their way through fears and doubts about the court case.

A pilot project in which alleged victims of domestic abuse were assigned such representatives led to a significant increase in conviction rates.

However, the white paper is not expected to include proposals floated last year to allow expert witnesses to explain the psychological impact of the crime on women in court.

The government examined whether this might help juries understand why some rape victims show little emotion when describing their ordeals in court. In some cases, defence lawyers have successfully argued that the woman’s behaviour is inconsistent with someone who has suffered such a trauma.

However, ministers have concluded that allowing psychologists to give evidence would be fraught with difficulty and could lead to an American-style “trial of expert witnesses”.

Times Recommends

• Donor organ allowed child’s own heart to heal
• Michael Jackson: Not the final chapter
• Brüno toned down for 15 rating