Gmail's latest redesign could put its 1.4 billion global users at risk of extortion by cyber criminals, US intelligence officials have warned.

The security risk to Gmail comes from a new feature, known as Confidential Mode, which may leave account holders vulnerable to 'phishing' attacks designed to extort their personal information or money.

Gmail is a free advertising-supported email service developed by Google, the US technology giant. Since its creation in 2004 Gmail has grown to become by far the world's most popular email service.

The new feature allows people to send emails that vanish after a set amount of time. To open them, the recipient must verify their identity by clicking on a link.

According to an intelligence note from the Department of Homeland Security seen by ABC News, the new feature has created an opportunity in which “malicious cyber actors could exploit the recent Gmail redesign”.

Their concerns surround the practice of "phishing", when con artists send emails pretending to be a legitimate company like a bank or service provider. The emails can be filled with malicious links that take victims to unsafe websites where they are asked to input personal account details that are often used to commit fraud.