People were being urged to ring 101 for emergencies on Sunday morning as 999 calls were not connecting to a number of police forces and fire services.
The warning was sent out after a technical fault affected the 999 calls. Durham Constabulary and the Tyne and Wear Fire and Rescue Service were among those to issue alerts.
They were urging people to ring 101 in an emergency until further notice. Durham Constabulary said: "We are currently experiencing issues with our 999 system, if an emergency and you are unable to dial 999 please use 101. If you have a medical emergency please dial 111. We are working to get this resolved."
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Northumbria Police posted on Facebook: "BT are experiencing issues all over the country with 999 lines - if you are trying to reach us and can not get through, please call 101 if it's an emergency.
"Any non emergency situations should be reported online via our website to help keep our lines free."
The North East Ambulance Service added: "The BT 999 phone lines system has been experiencing some issues this morning across the UK.
"Calls to 999 to access ambulance service in the North East are now working but if you have any problem accessing 999 for a medical emergency, please dial 111 instead. If your call is not urgent, please visit NHS111 online first."
The Tyne and Wear Fire and Rescue Service tweeted: "URGENT - Due to BT 999 failure - any emergency calls for Fire Service ring 101 where you will be put through to police who will pass this to us."
Among the other forces who tweeted a similar message were the Metropolitan Police, Greater Manchester Police, South Wales Police and Bedfordshire Police.
The Metropolitan Police said on Twitter: "Due to a technical fault that is impacting a number of police forces, many 999 calls are not connecting. Until further notice, please call 101 in an emergency. Please ONLY call in an emergency and please wait until later to make any 101 non-emergency calls."
Greater Manchester Police said: "BT have advised a number of forces that they are experiencing issues with their 999 lines that may affect connection to an emergency service. If your call is an emergency, please persevere with waiting for them to connect you. Non-emergency contact can be made online."
Just before 11am, BT confirmed that people can once again call 999 in an emergency after a nationwide technical fault.
BT said it had implemented a back-up platform after issues with 999 calls connecting were reported on Sunday morning.
Emergency services across the country have confirmed they are able to receive 999 calls again, but some warned they were still experiencing residual difficulties.
A spokesperson for BT said: “Early this morning we experienced a problem with the 999 service.
“The situation is fast-moving as we fix the problem and our back up platform is now working – so people should call 999 as usual. We will provide updates as the issue is resolved.”
