“One of the big questions when it comes to domestic spying is, ‘Who have been the NSA’s specific targets?’,” he said.

“Are they political critics and dissidents and activists? Are they genuinely people we’d regard as terrorists?

What are the metrics and calculations that go into choosing those targets and what is done with the surveillance that is conducted? Those are the kinds of questions that I want to still answer.”

Greenwald said the names would be published via The Intercept, a website funded by Pierre Omidyar, the billionaire founder and chairman of eBay. Greenwald left The Guardian, which published most of the Snowden revelations, last autumn to work for Omidyar.

“As with a fireworks show, you want to save your best for last,” Greenwald told GQ magazine. “The last one is the one where the sky is all covered in spectacular multicoloured hues.”