Police and prosecutors are failing to implement measures to boost the rape conviction rate, watchdogs have warned.
Ministers have long been concerned about low rape conviction rates
The police and the Crown Prosecution Service watchdogs said more effort should be made to build stronger cases.
Their report says too many rape claims in England and Wales are wrongly dismissed as unfounded.
Only 5% of reported rapes end in a conviction. The director of public prosecutions says he is "determined" to improve the way rape cases are handled.
Constitutional Affairs Minister Mike O'Brien said the government was considering a change in the law in an effort to raise the number of convictions.
Scale of false allegations over-estimated
Subjective judgements made about victims' credibility
CPS has no criteria for specialist rape prosecutors
Detection rates vary between 22% and 93% for different police forces
Inconsistency over the way forensic doctors examine victims
Lack of training for frontline officers
Authorities must challenge claims of consent "more vigorously"
Police and prosecutors should make better use of evidence showing defendant's "bad character"
He said: "Most people who are victims of rape know their perpetrator and the issue is therefore consent. What we need to do is make sure that the issue of consent goes before a jury."
The 175-page study of 752 reported rapes in 2005 was written by Her Majesty's Inspectorate of Constabulary (HMIC) and Her Majesty's Crown Prosecution Service Inspectorate (HMCPSI).
Police wrongly recorded rape allegations as "no crimes" in nearly a third of cases, it found.
Her Majesty's Assistant Inspector of Constabulary Huw Jones, one of the report's authors, said the conviction rate could be raised by "better equipping" witnesses in order to get the best evidence "right at the start".
One woman, Susan (not her real name), told the BBC she had an abortion after she was raped but her attacker was only convicted of assault. She said she was let down by prosecutors.
"You don't get any kind of legal representation or advice. I just felt in the dark as to what was happening and what I could do," she said.
In the Commons, Liberal Democrat leader Sir Menzies Campbell asked Prime Minister Tony Blair: "Isn't it time for a wholesale review of the law in this area, so as to ensure we provide proper protection for women and men, who are subject to this traumatic and violent assault?"
Mr Blair replied: "Of course, we already are looking at how we improve the conviction rate for rape.
"Over 50% of those cases are where there is either a partner involved or an ex-partner, and for those reasons I think it is obvious it will always be more difficult to secure a conviction."
Deputy Assistant Commissioner John Yates, of the Association of Chief Police Officers, said that in more than 85% of reported rapes the victim was known to the suspect but that these were the most difficult cases to prove.
"These are the cases that take place often behind closed doors where there are no other witnesses, where the forensic evidence is of limited value due to the consent issues," he said.
Director of Public Prosecutions Sir Ken Macdonald said: "I am determined to improve the way we deal with these cases from start to finish.
"We must make sure that we do what we are supposed to do when handling these cases."