Cheerful UK users of iCloud, Google Drive and other US-based services might do well to ponder this.

Cloud computing has exploded in recent years as a flexible, cheap way for individuals, companies and government bodies to remotely store documents and data. According to some estimates, 35 per cent of UK firms use some sort of cloud system – with Google Drive, Apple iCloud and Amazon Cloud Drive the major players.

But it has now emerged that all documents uploaded onto cloud systems based in the US or falling under Washington’s jurisdiction can be accessed and analysed without a warrant by American security agencies.

The Foreign Intelligence Surveillance Act, known as FISA, allows US government agencies open access to any electronic information stored by non-American citizens by US-based companies. Quietly introduced during the dying days of President George W Bush’s administration in 2008, it was renewed over Christmas 2012.

But only now are privacy campaigners and legal experts waking up to the extent of the intrusion.

Time for UK-based cloud services?