Female stars including fashion designer Victoria Beckham and Harry Potter author J.K. Rowling are joining forces to demand action to protect children in war zones.

The pair, along with British socialite Jemima Khan and other campaigners, have signed an open letter to the U.K. government calling for a new strategy to prevent sexual violence against women and children caught up in military conflict.

The letter, sent on behalf of the United Nations Children's Fund (Unicef) and published in The Times newspaper, urges British Foreign Secretary William Hague to press for action when he hosts the Global Summit to End Sexual Violence in Conflict, in London in June (14).

It reads, "In war zones, sexual violence is as devastating as bullets and bombs... One of the starkest reminders is Syria, where an entire generation is at risk of being lost as a fourth year of conflict and unimaginable atrocities approaches...

"International leaders must seize this opportunity to defend women and to commit to protect children in war zones from rape and sexual abuse. U.K. ministers must do their utmost to ensure that the summit prioritises measures to help children to report sexual crimes and hold their abusers to account. The U.K. must also secure more funding for psychological and long-term support for child survivors."