American intelligence agencies have been accused of spying on the emails of millions of Americans, including those of former president Bill Clinton.

In the latest in a series of intelligence scandals to hit Washington, details of a secretive email surveillance scheme are beginning to come to light - with fresh allegations reported in the New York Times.

The Times quotes one anonymous NSA analyst who claims that electronic messages sent to and from American citizens, and says that the former president - whose wife is now the country’s secretary of state - was among those targeted by the sweep.

The database system, called Pinwale, is used by America’s National Security Agency to intercept and examine huge volumes of email passing through American telecommunications networks.

The NSA has confirmed that Pinwale exists, although it will not comment on the latest allegations or give further details on how the system operates.