Domestic violence campaigners have raised concerns after a newspaper claimed plans to cut rapists' jail terms were being considered.
Men convicted of domestic violence may face courses instead of jail
Changes planned for England and Wales by the Sentencing Guidelines Council (SGC) must go out to consultation.
But the Observer says draft guidelines for judges will call for rape sentences to be cut by up to 15% because the SGC believes jail is now "more demanding".
Charity Refuge said it was a "backward step" and vowed to fight the plans.
Joanne Savage, secretary to the SGC, told the newspaper custodial sentences had become "more demanding".
Ms Savage told the Observer prisoners now spent at least half of their sentence behind bars and strict restrictions when released on licence could justify shorter sentences.
But shadow home secretary David Davis said: "To suggest today's prison regime is tougher than that of, say, 20 years ago is simply at odds with the facts.
"At a time when there is serious concern about the record of catching and convicting rapists, to reduce the deterrent can only make the problem worse.
"This proposal is wrong, both in the effect it will have and in the logic behind it."
The proposed SGC guidelines also say men convicted of domestic violence should be sent on courses aimed at changing their attitudes towards women instead of to prison, according to the newspaper.
But Ms Horley said the "ludicrous" plan would put lives at risk.
"The suggestion trivialises domestic violence, which is as serious if not more serious than any other violent crime," she said.
"Refuge is horrified that after 35 years of campaigning for the government and criminal justice system to take rape and domestic violence seriously that such proposals have been put forward."
The plan made "a mockery of government's commitments to address domestic violence which, after all, kills two women a week", Ms Horley said.
"It would be a travesty if the government accepted the SGC proposals on rape and domestic violence - they will put more women at risk," she added.
"They give licence to men to rape and batter women."
"We know that rigorous arrest, charging and sentences in custody for these crimes acts as an effective deterrent."
Established under the Criminal Justice Act 2003, the SGC is an independent body that aims to offer "authoritative guidance" on sentencing and "enable sentencers to make decisions on sentencing that are supported by information on effectiveness of sentences and on the most effective use of resources".
Initial proposals are put out to consultation before final versions are drawn up.
No one from the SGC, which advises all courts in England and Wales, was available to comment.