Google says it is expanding its policies to crack down on websites which trap users with "back button hijacking".

Back button hijacking is when a website interferes with a browser so the back button no longer takes users to the previous page, instead often keeping them on the site or presenting unsolicited ads.

In a blog post the tech giant behind the Chrome browser said it had seen a "rise of this type of behaviour" which had led it to act.

From 15 June the tactic will be deemed a "malicious practice", meaning sites which continue to adopt it may be down-ranked or even removed from Google Search results.

"Back button hijacking interferes with the browser's functionality, breaks the expected user journey, and results in user frustration," Google said in its post.

"People report feeling manipulated and eventually less willing to visit unfamiliar sites," it added.

Examples of practices it would clamp down on included sites using any technique which inserted "manipulative" pages into a user's browser history that stopped them from returning to the previous page.

Adam Thompson, director of digital at BCS, the Chartered Institute for IT, told the BBC: "Practices like back button hijacking undermine the basic user experience and break the expectations people have of how the web should work, so it's understandable that Google views this as a harmful behaviour and [is] taking action."

Google advised site owners which did not want to face the new penalties to ensure they did not do "anything to interfere with a user's ability to navigate their browser history", urging them to "thoroughly review their technical implementation".

It added sites which were penalised but then fixed the issue could submit a request to Google to have the demotion reconsidered.

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