Police would lose the power to unilaterally “drop” rape investigations, even if they think there is insufficient evidence to proceed, under Labour plans to revolutionise the way sexual crimes are handled.

At present there is no obligation for police to refer cases to the prosecutors before a decision is made to drop a case. But under proposals to be put forward by the shadow Attorney General Emily Thornberry on Monday, officers would have to get the agreement of the Crown Prosecution Service to end an investigation.

Ms Thornberry will say that she hopes the plan would end the culture of rape and sexual violence being an “optional” crime to investigate and help end a “culture of defeatism” where the authorities believe there will never be a large number of rape convictions because it is “too difficult” to prosecute.

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Ms Thornberry will make the announcement at Labour’s Women’s Safety Conference, which will also be addressed by the shadow Home Secretary Yvette Cooper. In an article for The Independent, Ms Cooper says Labour would also introduce compulsory sex- and relationship-education and turn the next generation of boys into “feminist” men.

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Ms Cooper said she believed the growth of internet porn was clearly linked to a rise of sexist abuse and violence in society. “We can’t ignore the way young people’s perceptions of sex and the interaction between men and women are being shaped by online access to extreme and violent porn,” she writes. “For years we have talked about the importance of empowering our daughters, giving them the confidence to challenge abuse and bringing them up as feminists. If we are going to achieve a real step-change in tackling violence against women, we need our sons growing up as confident feminists too.”

Ms Thornberry will point to figures showing that 21 per cent of rapists and over a quarter of domestic violence perpetrators are under 24. “We must ensure that the schools provide guidance and support and to push back against the relentless bombardment of objectification,” she will say.