Exclusive Google is blocking access to the entire NHS network, mistaking the amount of traffic it is currently receiving as a cyber attack.
An email from an NHS trust's IT department seen by The Register confirmed that the US search giant has mistaken the current traffic levels for a botnet.
The email headed "Google Access" stated: "Google is intermittently blocking access due to the amount of traffic from NHS Trusts Nationally (This is not being blocked by the IT Department).
"This is causing Google to think it is suffering from a cyber-attack.
"We are advising staff to use an alternative search engine i.e. Bing to bypass this problem.
"If you have 'Chrome' on your desktop the page will display correctly but if you 'should' get a CAPTCHA pop up, please follow the instructions to continue."
The source said they did not know why Google had suddenly decided to block access to the NHS net, but confirmed it was the "go-to resource" for a lot of clinicians.
The Register has contacted NHS Digital and Google for a comment.
Controversially, Google is also attempting to drum up business with the NHS through its DeepMind AI business.
Last year it emerged that the Royal Free NHS trust had signed a deal with DeepMind to give the outfit access to 1.6 million patient records, without explicit permission from patients.
It has since won a deal with Moorfields Eye Hospital to access one million anonymous eye scans.
The NHS is one of the biggest employers in the world, with 1.2 million people working for the organisation.
Earlier this week it emerged that a reply-all NHS email fail in Croydon resulted in 500 million emails being sent across the NHS in just 75 minutes.
Google refused to comment but said: "It is not correct to say we have blocked the entire NHS network." ®
Updated at 12:31 UTC on Wednesday 1 February to add: An NHS Digital spokesman contacted The Reg to say: “We are aware of the current issue concerning NHS IP addresses which occasionally results in users being directed to a simple verification form when accessing Google. This would appear to be due to the high number of people using our systems and trying to access Google at peak times. We are currently in discussion with Google as to how we can help them to resolve the issue.”