William Hague has defended the controversial initiative he established with Angelina Jolie, describing it as having made “enormous progress” in raising awareness and breaking taboos around sexual violence in conflict.

Set up by the former British foreign secretary alongside Hollywood actor Jolie, the project has encountered criticism since its glitzy London launch five years ago, and earlier this year was accused of losing momentum completely.

Talking to young film-makers about the Preventing Sexual Violence Initiative, Hague admitted it was “very difficult” to measure success in the face of the scale of the problem and spoke of “tens of thousands of people raped in war in South Sudan” and “hundreds of thousands in DRC”. But he said that films – like Jolie’s In the Land of Blood and Honey, which inspired the initiative – had the power to create empathy.

Asked what progress had been made, he said: “We’ve made a tremendous start, but it’s only a start because as things stand, no member of Isil or Boko Haram or the armed forces of Burma has been brought to trial for crimes of sexual violence.”

The Foreign Office, under whose remit the initiative sits, came under fire last year for failing to deploy its experts quickly in response to the widespread rape and of Rohingya women and girls.

Hague’s project has spent tens of millions over five years, and, he claimed, helped Britain lead the way on diplomacy in countries where sexual violence in conflict had taken place. It had led the UN to pass security council resolutions on the issue, he said, including getting 155 nations to sign up to action on the issue at the general assembly.

“There is no doubt we’ve made enormous progress in raising awareness,” he said. “In diplomatic action and in some countries taking specific actions.”

Prosecutions against perpetrators of sexual violence have taken place in Bosnia, DRC and Guatemala, he said, and the British army had been involved in military training on preventing sexual violence.

“We’ve broken a taboo, or are halfway through breaking a taboo … You would not have seen a few years ago a gathering of global film-makers like this on this subject.”

Hague and Jolie are calling for a new UN investigations unit to document and gather evidence, in the absence of security council agreement.

“I believe the United Nations, with British support, should set up an investigatory capacity, with the ability and capacity to document and gather evidence of crimes of sexual violence and similar crimes,” he said. “So even in cases where the UN security council can’t agree to take action, which is often the problem, nevertheless the evidence is gathered.”

The FCO said that it is exploring this and other options.