A senior British government official demanded the destruction of files held by London’s Guardian newspaper related to the US National Security Agency’s mass monitoring of phone and internet use, the newspaper’s editor said.

Alan Rusbridger, editor of the Guardian, which this year revealed a mass surveillance programme by US authorities, wrote last night that two months ago he was contacted by an official claiming to represent the views of the prime -minister.

“There followed two meetings in which he demanded the return or destruction of all the material we were working on,” he said. “The tone was steely, if cordial, but there was an implicit threat that others within government and Whitehall favoured a far more draconian approach.” Number 10 was not available for comment.