David Cameron appears to have given some ground on proposals to grant anonymity to those accused of rape.
In its coalition deal, the government backed keeping the identity of defendants in rape cases in England and Wales secret until after conviction.
But Mr Cameron told MPs he favoured a "limited extension" to the law to cover the period between arrest and charges.
Acting Labour leader Harriet Harman said she was still "disappointed" by the policy.
Raising the issue during the first session of prime minister's questions since the election, Ms Harman said even partial granting of anonymity would make it "harder" to bring rapists to justice.
At present, there are no restrictions on naming defendants who are over 18 years old.
In their coalition agreement, hammered out in the days following the general election, the Conservatives and Lib Dems said their government would "extend anonymity in rape cases to defendants", interpreted as applying at all stages before any conviction.
The proposal was not in either parties' manifestos but has been a Lib Dem policy since 2006.
Opponents of the proposals fear they would discourage rape victims from coming forward and do nothing to improve the conviction rate.
Describing the current conviction rate as a "scandal", Mr Cameron told MPs that all parties wanted to increase the number of successful rape prosecutions and to send more rapists to jail.
But he said he supported the conclusions of a review by the all-party Commons Home Affairs Committee - of which he was a member before 2005 - which recommended a "limited extension" of anonymity.
"We came to the conclusion that there was a case for saying that between arrest and charge there was a case for anonymity," he said, adding that rape victims were currently granted legal protection.
"The coalition agreement mentions this issue of anonymity. We will of course be bringing forward proposals that the House can then examine and debate.
"I understand what she says that it is important the publicity around a case can help bring other people who have been raped forward. I understand her case but I do think this does represent a good way forward."
He said MP would be given a chance to debate the proposed changes.
But Ms Harman said she disagreed with the government's approach.
"We know that it is often only after many rapes that a defendant is finally brought to court and it is only at that point, often, when previous victims find the courage to come forward," she said.
"To single out rape defendants sends a very powerful message to juries in rape cases that the rape victim is not to be believed. It sends a devastating message to rape victims that uniquely of all victims they are not to be believed."
Mr Cameron showed "no understanding of the progress that has been made on prosecuting rape and does not realise how seriously this will turn the clock back", she added.
Only 6% of all reports of rape to the police lead to a conviction, but more than half of the cases that make it to trial result in the suspect being found guilty, official figures show.
The anonymity proposal became Lib Dem party policy in 2006 after a number of cases in which celebrities were named in newspapers over allegations of sexual assault, even though in some cases they were not charged and the complainant was found to be malicious.
The 1976 Labour government introduced anonymity for defendants - only for the measure to be repealed 12 years later under the Tories.
A review of the law earlier this year warned there needed to be a proper examination of the wider issues.
There is no anonymity for defendants in Scotland and Northern Ireland.