Tulsi Gabbard, the US director of national intelligence, has hit out at the UK’s demand that Apple build a “back door” in its iCloud security system, saying such a move would be an “egregious violation” of Americans’ privacy that may breach the two countries’ data agreement.

Responding to a letter from Democratic Senator Ron Wyden and Republican congressman Andy Biggs, Gabbard said she shared their “grave concern” that it could allow British authorities to access Americans’ personal data and had instructed lawyers and intelligence officials to investigate the matter.

“I share your grave concern about the serious implications of the UK, or any foreign country, requiring Apple or any company to create a ‘back door’ that would allow access to Americans’ personal encrypted data,” Gabbard wrote to the US lawmakers. “This would be a clear and egregious violation of Americans’ privacy and civil liberties, and open up a serious vulnerability for cyber exploitation by adversarial actors.”