Across the local authority area, broadband speeds range from a superfast 93 megabits (Mbps) per second to a snail-paced 0.2 Mbps, according to data from Uswitch.com.
That means families using Zoom, Skype or Facebook to speak to relatives and friends could be faced with annoying freezes, cut-outs and sound delays.
It also means anyone downloading a movie could be left waiting up to 120 hours – compared to just one minute 20 seconds in nearby areas who enjoy the fastest speeds.
The average broadband speeds were collected in postcode areas with more than 50 addresses through at least one test in the 12 months up to October this year.
In total, nearly 400,000 tests were done.
They revealed, in Northumberland the postcodes with the slowest speeds were:
1) NE226DG, in Bedlington West, with an average speed of 0.2Mbps
2) TD152JA, in Berwick East, average 2Mbps
3) NE236TE, in Cramlington East, average 3.4Mbps
The postcodes with the fastest speeds were:
1) NE250RQ, in Hartley, average 93Mbps
2) NE233LW, in Cramlington North, average 89Mbps
3) NE236TL, in Cramlington East, average 78.4Mbps
Ernest Doku, broadband expert at Uswitch.com, said: “There is a digital divide that runs through Britain and it has has grown dramatically in the last year, with the fastest street’s broadband more than 5,000 times quicker than the slowest.”
He added: “It’s great that more of us are enjoying ultrafast broadband, but we don’t want to see large swathes of the country left behind on shoddy connections that aren’t suitable for modern life.”
The Government recently set out a draft strategy to connect one million homes and businesses with 1,000 Mbps broadband in some of the hardest-to-reach areas of the UK.
It is part of a plan to provide 85% of the country with broadband capable of the speed by 2025.
Minister for Digital Infrastructure, Matt Warman, said: "We will begin these procurements rapidly so broadband providers, big and small, can move quickly to get the job done and level up communities with this much faster, next generation broadband."