Fresh from the disaster on Friday, when the exchange was unable to trade following a technology problem, the organisation found itself dealing with a major security issue on its website.

An advert on the website, which has now been removed, was blamed for the problem. Users of the London Stock Exchange website who clicked on the advert could have allowed malware onto their computers.

The London Stock Exchange said there is nothing wrong with its website and there are no viruses. "We are waiting for Google to update its virus report."

In an e-mail to concerned customers the London Stock Exchange said: “Thank you for your e-mail and our apologies that you are having problems accessing our website. Unfortunately a third party advertising service provider which uses www.londonstockexchange.com has caused Google to display the error message you received. The London Stock Exchange's website itself has no issue and remains unaffected and entirely safe. As a precautionary measure all links to the third party service provider have since been removed from our website.

"We have requested that Google remove their warning as this issue is not in anyway related to our website and we have been assured this will be actioned shortly.

"Apologies for any inconvenience caused.”

This story was first published by Computer Weekly